Methods and apparatus for access to and/or treatment of the spine

ABSTRACT

Systems, devices, and methods suitable for use with procedures performed at least partially percutaneously are provided. In some procedures, two or more access devices for providing access to adjacent surgical locations within a patient are used. Certain embodiments of the access device comprise an elongate body having a distal end with one or more cutouts. The cutouts on adjacent access devices are generally aligned with each other to permit passage of a portion of a fixation element from one access device to the other access device. A fastener with an elongated removable head may be delivered to the surgical site through the access device. After a distal end of the fastener is secured to the surgical site, a portion of the elongated housing is detached from the remainder of the fastener and removed from the patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/760,551, filed Jun. 8, 2007, which claims the benefit of U.S.Provisional Patent Application No. 60/812,703, filed Jun. 9, 2006, andis related to U.S. Provisional Patent Applications No. 60/514,559, filedOct. 24, 2003, 60/545,587, filed Feb. 18, 2004, and 60/579,643, filedJun. 15, 2004. This application also is related to U.S. patentapplication Ser. No. 10/927,633, filed Aug. 26, 2004, now U.S. Pat. No.7,179,225, issued on Feb. 20, 2007, and is related to U.S. patentapplication Ser. No. 10/926,579, filed Aug. 26, 2004, now U.S. Pat. No.7,976,464, issued on Jul. 12, 2011. The entire contents of each of theforegoing applications is hereby expressly incorporated by referenceherein.

BACKGROUND

This application relates to surgical systems, assemblies, devices, andmethods that may be used for less invasive and/or minimally invasivesurgery, and in particular relates to surgical systems, assemblies,devices, and methods that may relate to gaining access to and/ortreatment of the spine.

Spinal surgery presents significant difficulties to the physicianattempting to reduce chronic back pain or correct spinal deformitieswithout introducing additional trauma due to the surgical procedureitself. In order to access the vertebrae to perform spinal procedures,the physician is typically required to make large incisions and cut orstrip muscle tissue surrounding the spine. In addition, care must betaken not to injure nerve tissue in the area. Consequently, traditionalsurgical procedures of this type carry high risks of scarring, pain,significant blood loss, and extended recovery times.

Systems, assemblies, devices, and methods for performing less invasiveand/or minimally invasive techniques have been proposed to reduce thetrauma of posterior spinal surgery by reducing the size of the incisionand the degree of muscle stripping in order to access the vertebrae. Anumber of different such systems, assemblies, devices, and methods areknown, each having certain advantages and disadvantages. However, thereis an ongoing need to provide alternative systems, assemblies, devices,and methods for gaining access to and/or treating the spine of apatient.

SUMMARY OF SOME EXAMPLE EMBODIMENTS

The invention provides several alternative systems, assemblies, devices,and/or methods for gaining access to and/or treating the spine of apatient.

Some example embodiments relate to an access device for providing accessto a spinal location within a patient. The access device may include anelongate body having a proximal portion and a distal portion and alength therebetween such that when the distal portion is positionedinside the patient adjacent the spinal location, the proximal portionextends outside the patient. The device may also includes a passageextending through the elongate body between the proximal and distalportions, and one or more channels and/or laterally facing openingsand/or cutouts in the distal portion that may be sized and/or configuredto permit a fixation element to pass through. In some exampleembodiments, the distal portion may be expandable from a firstnon-expanded configuration to a second, expanded configuration.

Some example embodiment relates to a spinal access assembly includingtwo or more spinal access devices, each access device having an elongatebody with a proximal portion and a distal portion and a lengththerebetween such that when the distal portion is positioned inside apatient adjacent a spinal location, the proximal portion extends outsidethe patient. The spinal access devices may also have a passage extendingthrough the elongate body between the proximal and distal portions, andone or both of the access devices may include one or more channelsand/or laterally facing openings and/or cutouts in the distal portionthat may be sized and/or configured to permit a spinal fixation elementto pass through. In some example embodiments, the distal portion of oneor both of the access devices may be expandable from a firstnon-expanded configuration to a second, expanded configuration.

Some example embodiments also relate to a spinal access and treatmentassembly that may include two or more spinal access devices, such as anyof those discussed 2) above, or hereinafter, and a spinal fixationelement, and two or more spinal fasteners configured to affix the spinalfixation element to vertebrae of a patient.

Additional embodiments relate to methods for treating the spine of apatient. Some such embodiments may involve the use of two or more accessdevices, for example, any of those discussed herein. One example methodmay include inserting a first access device through a first incision inthe skin of the patient, the first access device having a first proximalend and a first distal end and a first passage therebetween, wherein aportion of the first distal end has a first opening, and advancing thefirst access device until the first distal end is adjacent a firstspinal location. The method may also include inserting a second accessdevice through a second incision in the skin of the patient, the secondaccess device having a second proximal end and a second distal end and asecond passage therebetween, wherein a portion of the second distal endhas a second opening, and advancing the second access device until thesecond distal end is adjacent a second spinal location. A spinalfixation element having a proximal end and a distal end may be insertedthrough the first passage until the distal end of the fixation elementis adjacent the first spinal location. The distal end of the fixationelement may be advances through the first opening and through the secondopening to the second spinal location, until the proximal end of thefixation element is adjacent the first spinal location and the distalend of the fixation element is adjacent the second spinal location.

Another example method for treating the spine of a patient may includeadvancing a first access device into the patient such that a distal endof the first access device is adjacent a first spinal location, whereina portion of the distal end of the first access device may include achannel and/or cutout and/or laterally facing opening. The method mayalso include advancing a second access device into the patient such thata distal end of the second access device is adjacent a second spinallocation, wherein a portion of the distal end of the second accessdevice may include a channel and/or cutout and/or laterally facingopening. A fixation element having a proximal end and a distal end maybe inserted through the first access device until the distal end of thefixation element is adjacent the first spinal location, and the fixationelement may be advanced through the a channel and/or cutout and/orlaterally facing opening of the first access device and through thechannel and/or cutout and/or laterally facing opening in the secondaccess device, until the proximal end of the fixation element isadjacent the first spinal location and the distal end of the fixationelement is adjacent the second spinal location.

A further method for treating the spine of a patient may includeinserting a first retractor through a first incision in the skin of thepatient, the first retractor having a first proximal end and a firstdistal end and a first passage therebetween, wherein a portion of thefirst distal end may have a first channel and/or cutout and/or laterallyfacing opening. The method may also includes advancing the firstretractor until the first distal end is adjacent a first spinallocation, and inserting a second retractor through a second incision inthe skin of the patient, the second retractor having a second proximalend and a second distal end and a second passage therebetween, wherein aportion of the second distal end may have a second channel and/or cutoutand/or laterally facing opening. The method may also include advancingthe second retractor until the second distal end is adjacent a secondspinal location, and inserting a fixation rod having a proximal end anda distal end through the first passage and channel and/or cutout and/orlaterally facing opening of the first retractor and into the channeland/or cutout and/or laterally facing opening of the second retractoruntil the distal end of the fixation rod is adjacent the second spinallocation and the proximal end of the fixation rod is adjacent the firstspinal location.

Some example embodiments relate to a pedicle screw assembly. The screwassembly may include a threaded shaft, and a head including a housingand an elongated body. The housing may be attached to the elongated bodyat a frangible neck, and the elongated body may be adapted to be removedfrom the housing at the frangible neck. The housing may also beconfigured to receive a spinal fixation element. In some embodiments,the elongated body may have a length sufficient such that the elongatedbody extends above a patient's skin when the screw is secured to thepatient's vertebra.

In some embodiments, a breakoff pedicle screw assembly is disclosed, andmay include a threaded shaft, and a breakoff head that has a distalportion attached to the shaft and configured to receive a fixation rod,a neck region, and an elongated proximal portion. The neck region may beconfigured such that application of a sufficient amount of torque to theproximal portion causes the proximal portion to be separated from thedistal portion at the neck region. In some embodiments, the elongatedproximal portion may have a length sufficient such that the elongatedproximal portion extends above a patient's skin when the screw issecured to the patient's vertebra.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present invention.The Figures, and Detailed Description which follow more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages of the invention will becomeapparent from the following detailed description taken in conjunctionwith the accompanying figures showing illustrative embodiments of theinvention, in which:

FIG. 1 schematically illustrates an embodiment of an access device.

FIGS. 2-3 schematically illustrate an embodiment of a method andassembly for percutaneously performing a one-level spinal procedure.

FIG. 4 schematically illustrates an embodiment of a method and assemblyfor percutaneously performing a multi-level spinal procedure.

FIGS. 5-7 schematically illustrate embodiments of methods and devicesused to insert a fixation element.

FIG. 8 schematically illustrates an embodiment of acompressor-distractor instrument used with access devices.

FIGS. 9-12C schematically illustrate various embodiments of accessdevices with channels and/or cutouts and/or laterally facing openings.

FIGS. 13-14 are perspective views that schematically illustrateembodiments of a multipurpose tool and related apparatuses that can beused in surgical procedures.

FIG. 15 is a perspective view of an embodiment of a fastener.

FIG. 16 is a perspective view of an embodiment of a cap screw.

FIG. 17 is a perspective view of the embodiment of a multipurpose tooland fastener with the retaining clip of FIG. 18.

FIG. 18 is a perspective view of an embodiment of a retaining clip.

FIG. 19 is a perspective view of an embodiment of an anti-torque handlethat can be used with the multipurpose tool illustrated in FIGS. 13-14.

FIG. 20 is a perspective view of an embodiment of acompression/distraction link assembly.

FIG. 21 is a perspective view of the embodiment of thecompression/distraction link assembly of FIG. 20 in place on a pair ofmultipurpose tools.

FIGS. 22-23 are perspective view of another embodiment ofcompression/distraction link assembly in place on a pair of multipurposetools.

FIGS. 24-25 schematically illustrate various stages of an embodiment ofa spinal procedure.

FIGS. 26-27 schematically illustrate an example of a formation of atissue tunnel in a spinal procedure.

FIGS. 28-29 schematically illustrate embodiments of a passageway tooladapted to form a tissue tunnel.

FIGS. 30-32 schematically illustrate an example insertion of a fixationrod into a tissue tunnel.

FIGS. 33-34 schematically illustrate various example methods,assemblies, and aspects for inserting a fixation rod into a tissuetunnel.

FIG. 35 schematically illustrates dimensions and sizes of one embodimentof a multipurpose tool.

FIGS. 36A, 36B, and 37-39 schematically illustrate embodiments of screwinstallation tools.

FIGS. 40-41 schematically illustrate embodiments of apparatuses used inan example spinal procedure for at least partially percutaneouslydelivering an implant to a vertebral site.

FIGS. 42A-42B schematically illustrate an embodiment of a screw with abreakoff head.

FIGS. 43-46 schematically illustrate example methods for insertingembodiments of screws with breakoff heads and for removing the breakoffheads from the screws.

FIGS. 47-48 schematically illustrate various views of an embodiment of ascrew head removal tool that can be used to remove the breakoff heads,for example, from the example screws shown in FIGS. 42A-42B.

Throughout the figures, the same reference numerals and characters,unless otherwise stated, are used to denote like features, elements,components or portions of the illustrated embodiments. Moreover, whilethe subject matter of this application will now be described in detailwith reference to the figures, it is done so in connection with theillustrative embodiments. It is intended that changes and modificationscan be made to the described embodiments without departing from the truescope and spirit of the subject invention as defined by the appendedclaims.

DETAILED DESCRIPTION

Various embodiments of apparatuses and procedures described herein willbe discussed in terms of minimally invasive procedures and apparatuses,e.g., of endoscopic apparatuses and procedures. However, many aspects ofthe present invention may find use in conventional, open, and mini-openprocedures. As used herein, the term “proximal,” as is traditional,refers to the end portion of the apparatus that is closest to theoperator, while the term “distal” refers to the end portion that isfarthest from the operator.

The systems are described herein in connection with minimally invasivepostero-lateral spinal surgery. One such procedure is a two levelpostero-lateral fixation and fusion of the spine involving the L4, L5,and S1 vertebrae. In the drawings, the vertebrae will generally bedenoted by reference letter V. The usefulness of the apparatuses andprocedures is neither restricted to the postero-lateral approach nor tothe L4, L5, and S1 vertebrae. The apparatuses and procedures may be usedin other anatomical approaches and with other vertebra(e) within thecervical, thoracic, and lumbar regions of the spine. The procedures maybe directed toward surgery involving one or more vertebral levels. Someembodiments are useful for anterior and/or lateral procedures. Moreover,it is believed that embodiments of the invention are also particularlyuseful where any body structures must be accessed beneath the skin andmuscle tissue of the patient, and/or where it is desirable to providesufficient space and visibility in order to manipulate surgicalinstruments and treat the underlying body structures. For example,certain features or instrumentation described herein are particularlyuseful for minimally invasive procedures, e.g., arthroscopic procedures.As discussed more fully below, one embodiment of an apparatus describedherein provides an access device that provides retraction, allowsvisualization of a spinal location, and provides a passage for surgicalinstruments. In some embodiments, the access device acts as a retractor.In one embodiment the access device has an expandable distal portion. Inother embodiments, the access device is not expandable. In addition toproviding greater access to a surgical site than would be provided withdevice having a constant cross-section, the expandable distal portionprevents or substantially prevents the access device, or instrumentsextended therethrough to the surgical site, from dislodging or poppingout of the operative site.

Some of the systems and methods disclosed herein can be used to access asurgical location at or near the spine of a patient to enable procedureson the spine. These procedures can be applied to one or more vertebrallevels, as discussed herein. Additional procedures and combinations ofprocedures that may be performed using the systems described herein arediscussed below. In various forms, these procedures involve an anteriorlumbar interbody fusion, a minimally invasive lumbar interbody fusion,and other procedures particularly enabled by the access devices andsystems described herein. These procedures may be performed primarilythrough retractors or other similar access devices, such as thosediscussed herein. In some techniques, the procedures may be at leastpartially performed percutaneously, e.g., over a guidewire or otherstructure that has a smaller profile than the access devices describeherein. By performing at least a portion of the procedurespercutaneously, the amount of time that a retractor or similar accessdevice is deployed or expanded may be reduced. Also, percutaneoustechniques described herein increase the ability of the surgeon toquickly and easily deliver place markers, fasteners, and other implantsto target sites, to prepare target sites, and to complete procedures.Percutaneous techniques enable the performance of a substantial portionof a spinal procedure with little or no visualization of the locationwhere the procedure is performed.

Accordingly, it is desirable to provide systems, methods, and devicesfor percutaneous and partially percutaneous access that reduce tissuetrauma, require less surgical time, and reduce the need for fluoroscopyand image-guided assistance. In some embodiments, the systems, methods,and devices permit posterolateral fixation and/or fusion procedures tobe performed at least partially percutaneously.

In one embodiment, the system includes an access device that provides aninternal passage for surgical instruments to be inserted through theskin and muscle tissue of the patient to the surgical site. The term“access device” is used in its ordinary sense to mean a device that canprovide access and is a broad term and it includes structures having anelongated dimension and defining a passage, e.g., a cannula or aconduit. The access device is configured to be inserted through the skinof the patient to provide access during a surgical procedure to asurgical location within a patient, e.g., a spinal location. The accessdevice may provide distraction with or without having an expandablecomponent. The term “surgical location” is used in its ordinary sense(i.e. a location where a surgical procedure is performed) and is a broadterm and it includes locations subject to or affected by a surgery. Theterm “spinal location” is used in its ordinary sense (i.e. a location ator near a spine) and is a broad term and it includes locations adjacentto or associated with a spine that may be sites for surgical spinalprocedures.

One embodiment of the access device includes a wall portion defining areduced profile configuration for initial percutaneous insertion intothe patient. This wall portion may have any suitable arrangement. In oneembodiment the wall portion has a generally tubular configuration thatmay be passed over a dilator that has been inserted into the patient toatraumatically enlarge an opening sufficiently large to receive theaccess device therein.

The wall portion of the access device can be subsequently expanded to anenlarged configuration, by moving against the surrounding muscle tissueto at least partially define an enlarged surgical space in which thesurgical procedures will be performed. Accordingly, the expanded wallportion may act similarly to a dilator. Both the distal and proximalportion may be expanded. However, the distal portion may expand to agreater extent than the proximal portion, because the surgicalprocedures are to be performed at the surgical site, which is adjacentthe distal portion when the access device is inserted into the patient.

While in the reduced profile configuration, the access device defines afirst unexpanded configuration. Thereafter, the access device canenlarge the surgical space defined thereby by engaging the tissuesurrounding the access device and displacing the tissue outwardly as theaccess device expands. In some embodiments, the access device issufficiently rigid to displace such tissue during the expansion thereof.The access device may be resiliently biased to expand from the reducedprofile configuration to the enlarged configuration. In addition, theaccess device may also be manually expanded by an expander device withor without one or more surgical instruments inserted therein. Thesurgical site is at least partially defined by the expanded accessdevice itself. During use, the access device can move from a firstunexpanded configuration to a second expanded configuration.

In some embodiments, the proximal and distal portions are separatecomponents that may be coupled together in a suitable fashion. Forexample, the distal end portion of the access device may be configuredfor relative movement with respect to the proximal end portion in orderto allow the physician to position the distal end portion at a desiredlocation. This relative movement also provides the advantage that theproximal portion of the access device nearest the physician may remainsubstantially stable during such distal movement. In one embodiment, thedistal portion is a separate component that is pivotally or movablycoupled with the proximal portion. In another embodiment, the distalportion is flexible or resilient in order to permit such relativemovement. The access device is configured such that the proximal portioncan pivot in at least one direction with respect to the distal portion.

A. Methods and Devices for Spinal Access

As discussed above, the systems disclosed herein can be used to access asurgical location at or near the spine of a patient to enable procedureson the spine. These procedures can be applied to one or more vertebrallevels, as discussed herein. Additional procedures and combinations ofprocedures that may be performed using the systems described herein arediscussed below. In various forms, these procedures involve an anteriorlumbar interbody fusion, a minimally invasive lumbar interbody fusion,and other procedures particularly enabled by the access devices andsystems described herein. The procedures may be partially or completelyperformed percutaneously, e.g., over a guidewire or other structure thathas a smaller profile than the access devices describe herein.

Certain of the procedures described herein can be performed in partpercutaneously and in part minimally invasively, e.g., through an accessdevice. In some methods, a device that includes a hollow structure isused to form a percutaneous entry or path between the skin and avertebral surface or a vertebral target site. In other procedures, thepercutaneous entry or path may be formed between the skin of the patientand a suitable target site on or near the spine of the patient. Avertebral target site is any site on a vertebra at which a procedure ora portion of a procedure is to be performed. For example, as discussedbelow, some procedures may advantageously be performed at a pedicle of avertebra or at a region between a facet joint and a transverse processof a vertebra. In one technique the hollow structure of the percutaneousentry forming device is configured to receive a sharp implement, whichis configured to cut and separate tissue. As tissue is cut andseparated, the percutaneous access path can be formed between the skinand the vertebral surface.

In some percutaneous methods, cannulated fasteners (e.g., pediclescrews) are implanted through tissue over a guidewire to a vertebraltarget site, for example, the lumbar region of the spine. In someembodiments, after the fasteners are attached to the target site, afixation member (e.g., a rod or a plate) is implanted as part of afusion or fixation procedure. However, certain fixation memberimplantation methods require an additional incision and muscledissection for placement of the fixation member and/or require cuttingor splitting the tissue between the fasteners from the skin distally toplace and secure the fixation member. Also, some methods employ but maynot require fluoroscopic or image-guided assistance to place thefasteners at the target site.

Accordingly, it is desirable to provide systems, methods, and devicesfor percutaneous access that reduce tissue trauma, require less surgicaltime, reduce the need for fluoroscopy and image-guided assistance. Insome embodiments, the systems, methods, and devices permitposterolateral fixation and/or fusion procedures to be performed atleast partially percutaneously.

In certain embodiments, the methods involve creating a pedicle tunnel“percutaneously” using, for example, guidewires and implants andinstruments that can be delivered thereover. Additionally, one or moresuch methods can be at least partially performed through one or moresmall tubular retractors. In certain embodiments, the retractorscomprise an expandable portion as described herein. After the implantsare in place in each retractor, the distal portions of the retractorscan be adjusted to form a tunnel to permit a fixation member to beinserted proximally through one of the retractors and then positionedonto a fastener distally. In some embodiments, the tunnel is formed byexpanding the distal portions of one or more retractors. The fixationmember (e.g., a rod or a plate) can be positioned onto the fastenerwithout the need for an additional incision or muscle splitting. Abenefit of some embodiments of this method is that, where fixationassemblies are to be deployed on both sides of the spinous process, onlytwo small incisions per side of the spinous process are made for asingle-level procedure.

Some embodiments of the procedures disclosed herein reduce tissuetrauma, because less cutting and splitting of the muscles, fat, andfascia is required. In some procedures, an endoscope and/or lightingdevices for visualizing the anatomy can be positioned within one or moreof the tubular retractors. Additionally, manipulation of the fasteners(e.g., screw heads) for compression or distraction of the joint spacebetween the fasteners can also be performed with these methods.Embodiments of the methods disclosed herein are suitable for fixation orfusion procedures and may be used with any suitable spinal approach suchas, for example, a posterolateral approach.

The following is a non-limiting and nonexclusive list that comprisesactions that may be performed in one embodiment of a spinal surgicaltechnique (e.g., a one-level spinal fixation procedure). Additionaland/or different actions can be performed in other spinal proceduresaccording to other techniques. Further, the actions may be performed ina different order than shown, and some of the enumerated actions may beeliminated in other techniques.

One embodiment involves a method for an at least partially percutaneousspinal procedure. The procedure may include, for example, a fixation, afusion, and/or other suitable stabilization procedure. In this exampleprocedure, a trocar and needle (such as a Jamshidi needle or bone biopsyneedle) are percutaneously passed through the skin and into the targetedpedicle and into the vertebral body. The trocar and needle form apercutaneous access path that is sometimes referred to herein as atissue tunnel. In one technique, the trocar is inserted into the needleand the trocar and needle are advanced together through the skin at askin puncture location and through subcutaneous tissue (e.g., throughfat, muscle, and fascia) until a distal end of the trocar and needle areat the vertebral target site. The needle and trocar thus create a tissuetunnel through subcutaneous tissue. In one method, a generallyposterolateral approach is employed and the initial advancement of theneedle and trocar positions the needle and trocar at the pedicle of thetarget vertebra. Advancement of the needle and trocar may be aided byfluoroscopy, e.g., using a C-arm or other similar technique.

After a percutaneous entry, or percutaneous entry path, has been createdthrough the skin and subcutaneous tissue, the vertebral target site maybe prepared, if desired. In one method, the needle and trocar areadvanced further into the target vertebra at the vertebral target siteto form a tunnel in the target vertebra. The tunnel may be formed in thepedicle and is sometimes referred to as a pedicle tunnel. A proximal endof the trocar remains outside the patient, above the skin puncturelocation throughout the target site preparation. Preparation of thevertebral target site may include further procedures, such as tapping ofthe pedicle tunnel.

In one embodiment, the trocar is removed, leaving the needle in thepedicle. A guidewire, or other elongate body, is inserted into theproximal end of the needle. The guidewire may be advanced through thetissue tunnel and through the pedicle tunnel within the needle. In oneapplication, the guidewire is advanced until a distal end of theguidewire is located in the vertebral body of the target vertebra. Theguidewire extends proximally from of the skin and of the proximal end ofthe needle. The needle is removed leaving the guidewire in place,extending distally into the pedicle tunnel and proximally out of theskin.

Optionally, it may be advantageous to prepare the pedicle tunnel byforming threads within the tunnel. One method of forming threads in thepedicle tunnel involves tapping the pedicle tunnel with a cannulatedtap. A cannulated tap is a low profile instrument that has an elongatebody and an outside surface. The elongate body extends between aproximal end and a distal end. A bore, or cannulation, is formed throughthe elongate body between the proximal and distal ends. The elongatebody has formed thereon a structure configured to form internal threadswithin the pedicle tunnel, e.g., on the outer surface. The cannulatedtap may be advanced over, e.g., slid over, the guidewire until thedistal end is at the vertebral target site. Thereafter the cannulatedtap may be rotated about the guidewire and advanced, turning thecannulated tap into the pedicle tunnel. As the cannulated tap advancesthe threads are formed in the pedicle tunnel. Tapping creates threads inthe pedicle tunnel that will mate with corresponding threads on animplant to be inserted later.

In some applications, further dilation of the percutaneous access pathor entry facilitates insertion of an implant. In one technique, a smallincision is created at the skin puncture location. In one technique, anincision is created that is about 5-15 mm long. In some variations, anincision that is less than 5 mm can be created. The incision also canextend a distance into the tissue beneath the skin. The incisionfacilitates the insertion of one or more dilators (or obturators) overthe wire to increase the size of the percutaneous access path or entry.The dilator may be advanced at least a substantial portion of thedistance from the skin puncture location to the surface of the vertebrato reduce the resistance of the tissue beneath the skin to the insertionof an implant. The dilators are removed prior to insertion of an implantin one technique. The dilators/obturators may be inserted at the accesssite to create a tunnel through the tissue to the pedicle.

Although significant advantages are realized by preparing the vertebraltarget site prior to insertion of an access device, blood and other bodyfluids and tissues can hide or obscure the location of the preparedsite. After the percutaneous access path or entry has been created, amarker may be delivered over the guidewire to the vertebral target site.Placing a marker within the pedicle tunnel aids the surgeon in findingthe pedicle tunnel later in the procedure. Further details of a markersuitable for use with methods discussed herein is disclosed in U.S.patent application Ser. No. 11/184,568, filed Jul. 19, 2005, titledMETHODS AND APPARATUSES FOR PERCUTANEOUS IMPLANT DELIVERY, which ishereby incorporated by reference herein in its entirety.

In one method, an access device is inserted into the patient to encloseone or more of the adjacent pedicles in a working space so that aminimally invasive portion of a procedure may be performed. Inparticular, an incision may be created by connecting, by extending, orby connecting and extending the incisions made for the guidewires. Afterthe incision is made, the tissue may be dilated, and an access device ora retractor may be inserted over the dilator (or obturator). In someembodiments, the access device comprises an expandable distal portionthat may be expanded so that the distal portion extends over one or moreof adjacent pedicles (and any previously inserted markers). Two tubularretractors may be inserted at two adjacent vertebral sites. In sometechniques, after the access device is inserted over the dilator orobturator (or a series of these), the dilator(s) or obturator(s) areremoved, leaving the guidewire in place within the access device.

In one technique, a fastener such as, for example, a cannulated pediclescrew, is inserted over a proximal end of the guidewire. A cannulatedscrewdriver device can be used to move the fastener through the accessdevice to the vertebral site, where it can be attached to the pedicleand vertebral body (e.g., by screwing with the cannulated screwdriver).In one method, after insertion and attachment of the fastener, thescrewdriver and the guidewire can be removed, leaving the fastener andaccess device in place.

In some methods, after a first fastener is attached to a first vertebralsite (and the guidewire removed), the above techniques are repeated sothat a second fastener is attached to a second vertebral site and so on.However, in other methods, a trocar, needle, and guidewire are installedat each of the vertebral sites (e.g., at each pedicle), and then thesubsequent acts of expanding the surgical site with a dilator/obturator,inserting the access device, and securing a fastener to the vertebralbody (e.g., at a pedicle) are performed.

Each access device is oriented properly and expanded distally to allowmating openings of the distal portion to align and create a short tunnelfor passing a rod or other fixation element between access devices. Thescrew heads are oriented and aligned with the tunnel to receive the rod.The rod is then placed proximally though one of the access devices andis targeted and positioned to the tunnel opening by a variety of means(e.g., rod holder, slide-like guide, suture thread, wire or cable,etc.). The rod is manipulated (by pushing or pulling or a combination ofthese) through the tunnel from one access device to the next (andsuccessive retractors if more than 1-level) until the rod is positionedand seated in all screw heads in preparation for placement of a securingmeans (e.g., cap screw). The rod is secured to each screw head usingfixating and delivery instrument means through each access device.Instruments such as countertorque drivers, torque limiting instrumentsand compressor/distractor instruments may be utilized as desired by thesurgeon. Bone graft may be placed through the tubes and around thescrews and connecting member as desired.

It is appreciated that many variations of this method are possible andthat the actions described herein can be performed in many ways and inmany orders so as to enable access to the vertebral sites. For example,a one-level procedure may involve delivering two fasteners (e.g.,pedicle screws) to two adjacent vertebral sites (e.g., L4 and L5) usingtwo access devices.

In certain embodiments, the access device provides an internal passagefor surgical instruments to be inserted through the skin and muscletissue of the patient to the surgical site. The access device has a wallportion defining a reduced profile, or low-profile, configuration forinitial percutaneous insertion into the patient. This wall portion mayhave any suitable arrangement. In one embodiment, the wall portion has agenerally tubular configuration that may be passed over a dilator thathas been inserted into the patient to atraumatically enlarge an openingsufficiently large to receive the access device therein. In somemethods, the distal portion of the access device is expanded prior toinsertion of a fastener into the access device, while in other methodsthe distal portion is expanded at a later stage of the procedure.

In some embodiments, the proximal and distal portions of the accessdevice are separate components that may be coupled together in asuitable fashion. For example, the distal end portion of the accessdevice may be configured for relative movement with respect to theproximal end portion in order to allow the physician to position thedistal end portion at a desired location. This relative movement alsoprovides the advantage that the proximal portion of the access devicenearest the physician may remain substantially stable during such distalmovement. In one embodiment, the distal portion is a separate componentthat is pivotally or movably coupled to the proximal portion. In anotherembodiment, the distal portion is flexible or resilient in order topermit such relative movement.

FIG. 1 schematically illustrates an embodiment of an access device 100that can be used with the methods disclosed herein. In this embodiment,access device 100 has a tubular configuration with an expandable distalportion 110 configured to have one or more rod delivery channels 130(e.g., “cut outs” or “mating openings” and/or “laterally facingopenings”) that are sized and shaped to permit a fixation element (e.g.,a rod or a plate) to pass therebetween. In some embodiments, thechannels or cut-outs 130 are in a side wall of the expandable distalportion 110. In other embodiments, laterally facing openings 130 permita fixation element to pass through. In further embodiments, the accessdevice 100 has two or more cut-outs 130 in opposing sides of the distalportion 110. FIG. 2 schematically illustrates the placement of fixationelement 140 (shown as a rod) through channels 130 in an example of aone-level procedure involving two access devices 100 positioned oververtebrae V. Similar methods may involve the placement of three, four,or more access devices to provide access to multiple spinal locations,and may involve multi-level procedures.

Some example structures and/or configurations of access devices that canbe used with the methods disclosed herein are disclosed in U.S. patentapplication Ser. No. 10/926,579, filed Aug. 26, 2004, published asPublication No. U.S. 2005/0273131 A1, U.S. patent application Ser. No.10/927,633, filed Aug. 26, 2004, now U.S. Pat. No. 7,179,225, U.S.patent application Ser. No. 10/845,389, filed May 13, 2004, entitled“Access Device For Minimally Invasive Surgery,” in U.S. patentapplication Ser. No. 10/658,736, filed Sep. 9, 2003, U.S. patentapplication Ser. No. 10/117,440 (filed Apr. 5, 2002, published Oct. 9,2003 as Publication No. U.S. 2003/0191371A1), Ser. No. 10/180,658 (filedJun. 26, 2002, published Jan. 1, 2004 as Publication No. U.S.2004/0002629A1), Ser. No. 10/792,358 (filed Mar. 3, 2004, published Sep.9, 2004 as Publication No. U.S. 2004/0176665A1), which are herebyexpressly incorporated by reference herein in their entireties. Inaddition, such assess devices as disclosed therein may be modifiedand/or may include one or more channels 130 (e.g., “cut outs” or “matingopenings” and/or “laterally facing openings”) as discussed above.

In one method, first and second access devices are oriented so that thechannels 130 are generally facing or aligned with each other as shown inFIG. 2. In techniques using one or more expandable access devices 100,an expandable distal portion 110 of the access device may be expanded tocreate a short tunnel that permits passage of a fixation element 140.Portions of the fasteners 150 (e.g., the pedicle screw heads) may beoriented and aligned with the tunnel so as to receive the fixationelement 140.

The fixation element 140 (e.g., the rod shown in FIG. 2) is then placedproximally through one of the access devices 100 and can be moved to thetunnel opening using a variety of devices and/or techniques. Thefixation element 140 may be a rigid element, such as a rigid rod orplate. In another embodiment, the fixation element 140 may be a flexibleelement that enables the adjacent vertebrae to maintain a degree oftheir natural range of motion. Additional structure related to flexiblefixation elements and technique for application of such elements are setforth in U.S. patent application Ser. No. 10/693,815, filed Oct. 24,2003, which is hereby incorporated by reference herein in its entirety.

For example, FIG. 2 schematically shows the fixation element 140 beingpushed into and through the tunnel with a rod inserter 160.Alternatively, a rod holder, a slide-like guide, a suture thread, wire,or cable can be used to push (and/or pull) the fixation element from oneaccess device, through the tunnel, to the next access device.

The fixation element 140 can be manipulated by pushing or pulling (or acombination of pushing and pulling) from one access device 100 to thenext, through the tunnel. If a multilevel procedure is performed, thefixation element 140 can be manipulated through successive accessdevices 100. In certain methods, the fixation element 140 is positionedand seated in the fasteners 150 (e.g., within the screw heads) inpreparation for placement of a securing means (e.g., a cap screw). Thefixation element 140 is secured to each of the fasteners 160 usingfixating and delivery instruments and device inserted through the accessdevices 100. For example, devices such as countertorque drivers, torquelimiting instruments, and compressor-distractor instruments may beutilized by the physician. In some methods, bone graft may be placedthrough the access devices 100 and disposed around the fasteners 150 andfixation elements 140 as needed to enhance the growth of bone betweenthe fasteners 150 and the fixation elements 140 and between theseelements and adjacent vertebrae V. FIG. 3 schematically illustrates thecompleted one-level construct prior to the removal of the access devices100. A second one-level construct can be applied to the spine on theother side of the spinous process.

One-level, two-level, and more than two-level (e.g., three-level andother multi-level) procedures are contemplated. FIG. 4 schematicallyillustrates multilevel constructs utilizing three access devices 100,200, 400. As shown in FIG. 4, in certain methods the center accessdevice 200 may have channels 230 (e.g., “cut outs” or “mating openings”and/or “laterally facing openings”) on opposite sides of the distal wallportion. In some embodiments, the channels 230 are arranged to be about180 degrees apart. The use of such a “double slotted” access device 200advantageously permits a fixation element 140 (e.g., a rod) to passentirely through the center access device 200 so as to engage fasteners150 disposed on adjacent vertebrae V. In some of these methods, each ofthe access devices 100, 200, 400 is oriented so that its channels 130,230, 430 are generally aligned with the channels on the other accessdevices. This orientation provides a tunnel that is suitable for passageof the fixation element 140 through all of the access devices 100, 200,400 in a multilevel procedure.

FIG. 4 schematically illustrates various access devices suitable for usein single- or multi-level procedures. A distal portion of the accessdevice 100, 200, 400 is configured with one or more slots, holes, cutouts, openings, channels, or tunnels 130, 230, 430. In some embodiments,the slots are disposed on one side of the distal portion of the accessdevice, while in other embodiments the slots are disposed on both sides(e.g., about 180 degrees apart). In yet other embodiments, slots may bearranged at other positions around the access device in either a uniformor non-uniform distribution of positions. As described with reference toFIG. 4, a two-sided slotted access device is particularly advantageousin multilevel procedures because the mutually opposed slots permitpassage of the fixation device 140 entirely through the access device200 (see FIG. 4). The distal portion of the access device may beexpandable, as shown in access device 400, or not expandable, as shownin access devices 200, 100. Many variations are possible. For example,FIG. 4 schematically illustrates one multilevel method that utilizesthree access device variations: a one-sided slotted expanding retractor400, a two-sided slotted non-expanding retractor 200, and a one-sidedslotted non-expanding retractor 100. In other embodiments, the distalportion of the access device does not expand, but is configured to pivotor rotate about a pivot point.

Although the methods discussed with reference to FIGS. 1-4 illustrate aposterolateral lumbar spinal surgery procedure through an access device,in other embodiments, similar methods can be used for other regions ofthe spine (e.g., cervical and thoracic regions), and other approachesmay be used (e.g., anterior, lateral, and retroperitoneal). Manyvariations are possible without departing from the scope of the methodsdisclosed.

FIGS. 5-7 schematically illustrate embodiments of methods and devicesthat can be used to insert and position a fixation element 140 during aspinal procedure. In FIG. 5, a suture passer instrument 170 or a needleis used to pass a flexible pulling member such as a suture, wire, cable176, or other suitable connecting element, through a tunnel formedbetween two slotted access devices 100. The suture passer 170 isinserted into a first access device 100 and used to position the suture176 at a slot or cut out 130 at a distal end 110 of the first accessdevice 100. The suture passer 170 can be configured with a rounded orhooked end portion 172 that can be pushed partially or totally throughthe tunnel so as to provide access to an end of the suture 176 in asecond access device 100. A grasping instrument 180 can be used to grabor hold the end of the suture 176 and pull it through the second accessdevice 100. In some embodiments, the suture passer instrument 170 has athumbwheel 174 configured so that rotation of the thumbwheel 174 causesthe suture 176 to be advanced through the suture passer 170.

After a portion of the suture 176 is inserted through the access devices100 and the tunnel formed therebetween, an end of the suture 176 may beattached to a fixation element or rod 140. See FIG. 6. The attachmentmay be via an attachment element 178 such as an eyelet, finger trapsuture, a flexible cap, clamp or other attachment means, or the like.After attachment, the fixation element 140 may be positioned in thetunnel between the access devices 100 by pulling on the suture 176. Insome embodiments, the fixation element 140 is cannulated and passes overthe suture 176. After attachment of the suture, the fixation element 140is positioned in the tunnel between the access devices 100 by pulling onan opposite end of the suture 176. In some methods, additionalinstruments, such as grasper apparatus 180, may be used to assist inpositioning the fixation element 140.

FIG. 7 illustrates an alternative method to insert a fixation element140. In this method, a guide 190 is used to position the fixationelement 140 within the tunnel between the access devices 100. In certainembodiments, the guide 190 is a slotted “slide” to permit the physicianto slide the fixation element 140 toward the distal end of the guide190. In some embodiments, the guide 190 has a concave configuration forreceiving and guiding the fixation element 140 through the passage inthe access device 100. The guide 190 may have a curved distal end tofacilitate guiding the fixation element through a cut-out 130 or openingin the access device. In one technique, the one or more access devices100 can be pivoted so as to help position the guide 190.

Additional instruments, devices, and apparatuses can be used in thefixation or fusion procedures. For example, FIG. 8 schematicallyillustrates a compressor-distractor device 250 that can be used to shiftthe vertebrae prior to final securing of the fixation element 140 to thefasteners 150 attached to the vertebrae.

FIGS. 9-12C illustrate several embodiments of access devices that can beused with the percutaneous methods discussed herein. FIGS. 9-10schematically illustrate side views (FIG. 9) and end views (FIG. 10) ofan expanding access device 300 comprising a distal end 310 that ispivotally attached to a tube portion 320, e.g., via one or more rivetsor pins or protrusion. The distal end 310 comprises at least one slot315 that can slide around a pin or rivet 317 attached to the tubeportion. In a contracted configuration, the distal end 310 is pivotedinwards so that the pin or rivet 317 engages one end of the slot 315. Inan expanded configuration, the distal end 310 is moved away from thetube portion 320 so that the pin or rivet 317 engages the other end ofthe slot 315. The length of the slot 315 and the position of the pin orrivet 317 can be adjusted to provide for differing amounts of expansion.FIGS. 9-10 also show example dimensions and sizes of certainembodiments, but these dimensions and sizes are not intended to belimiting. For example, various embodiments provide for expansion of thedistal end to a diameter (d) of about 20 mm to about 35 mm. Also, therelative size or length of the distal end can be selected to providesuitable expansion. In this embodiment, the distal end comprises a cutout area 330 sized so that a fixation 140 element can pass through thecut out area 330. For example, the cut out 330 may have a height (c)from about 10 mm to about 20 mm and a width (e) from about 5 mm to about20 mm in certain embodiments. In this embodiment, a cut out area 330 isshown on one side of the access device 300. In other embodiments, cutout areas 330 may be included on both sides, or on other portions of thedistal end.

The tube portion 320 has a proximal end, which in some embodiments, hasan inner diameter (b) in a range from about 12 mm to about 20 mm. Incertain embodiments, the tube portion may contain a cut out area on aside of the tube opposite to the distal end. The tube portion may have alength that permits the proximal end to extend outside the body when thedistal end of the retractor is adjacent a vertebral target location. Thelength (a) of the expanding access device 300, from the distal end tothe proximal end of the tube portion 320 may be in a range from about 50mm to about 120 mm in various embodiments. Other sizes, lengths, anddiameters are possible.

FIGS. 11A-11D schematically illustrate an alternate embodiment of anexpanding access device 400 comprising a tube portion 420 and a distalskirt 410 that is pivotally connected to the tube portion 420. FIGS. 11Cand 11D are end views of FIGS. 11A and 11B, respectively. The tubeportion 420 is elongated and comprises a wall 422 that is generallycylindrical in cross-section. The wall 422 defines a passageway thatextends therethrough to permit passage of implants and instruments. Aportion of the distal end of the wall 422 is cut off to permit access inan expanded configuration. The skirt 410 overlaps the cut off portion424 of the distal end of the wall 422 and is pivotally attached to thetube portion 420 by, e.g., one or more rivets 412. In some embodiments,the skirt 410 comprises at least one arcuate slot 415 that is configuredto slide around a pin 417 disposed on the tube portion 420 (FIGS. 11A,11B). In a contracted configuration (FIGS. 11A, 11C), the skirt 410 ispivoted inward toward the tube portion 420 so that the pin 417 isadjacent one end of the arcuate slot 415. In an expanded configuration(FIGS. 11B, 11D), the skirt is pivoted outward about the rivet, awayfrom the tube portion, such that the pin is adjacent the opposite end ofthe arcuate slot. Accordingly, in the expanded configuration the distalend of the access device 400 has a larger cross-sectional area than inthe contracted configuration.

In certain embodiments, the skirt 410 comprises one or more openings 430or cut out areas (e.g. “channels” or “mating openings” and/or “laterallyfacing openings” that permit at least a portion of a fixation element topass therethrough. The cut out area 430 is formed in a region of theskirt 410 that pivots farthest away from the tube portion 420. The cutout area 430 can have any suitable shape and size to permit passage ofthe fixation element. The alternate expanding access deviceschematically shown in FIGS. 11A-11D generally has dimensions similar tothe expanding access device 300 schematically illustrated in FIGS. 9-10.

FIGS. 12A-12C schematically illustrate embodiments of non-expandingaccess devices 500, 550. FIGS. 12A and 12B illustrate access devices 500with cut outs 530 (e.g. “channels” or “mating openings” and/or“laterally facing openings”) on two sides, whereas FIG. 12C illustratesan access device 550 with a single cut out 530 on one side. In theseembodiments, the cut out 530 has a generally upside-down “U”-shapedcross-section. Other cross-sectional shapes are possible. For example,FIG. 10 illustrates a cut out 330 with more rounded corners. In yetother embodiments, the cut out can be, for example, circular, oval,triangular, or rectangular. Access devices with cut outs on two sidesare particularly suitable as a center access device in a multilevelprocedure.

Additional embodiments of devices and components can be used for theseor other procedures on the spine. For example, some of these proceduresmay be single- or multi-level fixation or fusion procedures at targetlocations on or near the vertebrae. In certain procedures, at least partof the procedure is performed percutaneously. Other parts of theprocedure may be performed minimally invasively, e.g., through an accessdevice.

B. Methods and Devices for Spinal Access Using a Multipurpose Tool

FIGS. 13 and 14 schematically illustrate a multipurpose tool 700 thatcan be used with any of the procedures discussed herein. For example,the multipurpose tool 700 can be used for purposes such as to assistinstallation of fasteners onto target sites and/or to assist guiding afixation element (e.g., a fixation rod) into engagement with thefasteners. Although in some procedures, embodiments of the multipurposetool 700 are used for several purposes, it is recognized that in otherprocedures, embodiments of the multipurpose tool are used for only asingle purpose. Accordingly, a skilled artisan will understand that anembodiment of the multipurpose tool 700 can be configured for onepurpose or for two purposes or for three or more purposes in varioustechniques, and the multipurpose tool 700 is not to be limited only tothose embodiments configured for more than one purpose.

In some embodiments, the multipurpose tool 700 comprises an elongatebody 710 with a proximal end 720 and a distal end 730. The elongate body710 defines a bore or passageway 740 between the proximal and distalends of the tool. In certain embodiments, the elongate body 710comprises a generally cylindrical portion at the proximal end 720 of thetool and at least two arms 750 that extend from the cylindrical portiontoward the distal end 730 of the tool. The arms 750 are spaced apartfrom each other and define elongated slots 760 therebetween. In someembodiments, the slots 760 extend substantially along the length of theelongate body 710. The multipurpose tool 700 may have a transversecross-section that is generally circular, and the arms 750 havecorresponding arcuate cross-sections. In some embodiments, the arms 750have substantially similar shapes and sizes and the slots 760 aresymmetrically disposed about the circumference of the elongate body 710.In certain embodiments, the multipurpose tool 700 comprises two arms 750that define a pair of opposed slots 760. In some embodiments, the widthof each of the slots 760 measured circumferentially is typically lessthan the width of each the arms 750. Although two arms 750 and two slots760 are shown in FIGS. 13-14, in other embodiments a different number ofarms is used such as, for example, three arms, four arms, or five arms.Further, in some embodiments, the length of each of the slots may bedifferent. For example, one of the slots may extend substantially alongthe length of the tool, while another slot may be shorter.

The multipurpose tool 700 generally is fabricated from a substantiallyrigid material such as a metal or a plastic. The material should besufficiently flexible and/or resilient so that the arms 750 tend toreturn to their initial position after a displacement. In someembodiments, the tool is fabricated from titanium or stainless steel,although other metals can be used such as, for example, nitinol.

In certain procedures, the multipurpose tool 700 is used to grasp andhold other devices or components. For example, in the embodiment shownin FIGS. 13-14, the distal end 730 of the multipurpose tool 700 has aprotrusion 770 (FIG. 13) configured to engage a fastener such as, forexample, a pedicle screw assembly. The multipurpose tool 700 can be usedto deliver the fastener to a target location on the spine of a patientthrough, for example, a percutaneous path or channel formed in thetissue of the patient. FIG. 15 illustrates an embodiment of a fastener800.

The fastener 800 may be used as a bone anchor such as, for example, apedicle screw, although in other embodiments, the fastener 800 may beconfigured for attachment to other vertebral landmarks such as, forexample, a facet joint, a transverse or spinous process, or othersuitable location. As shown in FIG. 15, the fastener 800 comprises ascrew portion or shaft 810 and a head or housing 820. The shaft 810 hasa distal threaded portion configured to be inserted into a hole, whichmay be tapped, in the vertebra at the target location. The head 820 isattached to a proximal end of the shaft 810 and is configured to receivea fixation element (e.g., a fixation rod). In one embodiment, the head820 comprises two flanges 822 that define a generally “U”-shaped openingformed therebetween. In use, a portion of the fixation element is placedin the U-shaped opening between the flanges 822 and is secured by, forexample, a cap screw or set screw 900 (FIG. 16). As shown in FIGS.15-16, an inner surface 824 of the head 820 may be threaded to receivethe externally threaded cap screw 900, which is screwed into the head820 so as to secure the fixation element within the head. In someembodiments, the fastener 800 is cannulated, e.g., it has an internallumen configured for a guidewire or the like to pass therethrough sothat it may be delivered to the target location.

In other embodiments, the head comprises a housing having a firstpassage configured to receive a screw portion and a second passage witha longitudinal axis extending transverse to the first passage. The screwportion extends through an opening in the housing into the secondpassage and is movable to the housing. For example, the screw portioncan be positioned in any of a plurality of desired angular positionswith respect to the longitudinal axis of the second passage. Furtherdetails of fasteners suitable for use with the systems and methodsdisclosed herein can be found in U.S. patent application Ser. No.11/415,676, filed May 2, 2006, titled “METHODS FOR CONNECTING ALONGITUDINAL MEMBER TO A BONE PORTION,” which is hereby incorporated byreference in its entirety and made part of this specification.

In some embodiments, the fastener 800 is configured to engage themultipurpose tool 700. For example, the head 820 may include one or morerecess or detent feature 830 configured to mate with a correspondingprotrusion 770 in the multipurpose tool 700. In the embodiment shown inFIG. 15, the detent feature 830 is a cylindrical hole through the flange822 that is sized and shaped to mate with a corresponding cylindricalprotrusion 770 formed on the inner surface of at least one of the arms750 of the multipurpose tool 700. The depth of the detent feature 830 isgenerally about the same as the extent of the protrusion 770 on theinner surface of the arms 750. In other embodiments, the protrusion 770can comprise a dimple, a bump, a ridge, or some other suitable shape. Insome embodiments, each of the arms 750 of the multipurpose tool 700includes a protrusion 770 that can mate with a corresponding detentfeature 830 on the head 820 of the fastener 800. For example, in theembodiment show in FIG. 15, each flange 822 of the head 820 comprises adetent feature 830 that mates with a protrusion 770 on each of the arms750. In other embodiments, the fastener 800 can be grasped by themultipurpose tool 700 via other mechanisms. For example, the distal endsof the arms may have a rim that is configured to engage a correspondinggroove in the head. Many other variations are possible.

In one embodiment, coupling the fastener 800 to the multipurpose tool700 involves the user grasping the multipurpose tool 700 and applying aforce to urge the arms 750 slightly apart until the protrusions 770 canfit around the head 820 of the fastener 800. The user manipulates theposition and orientation of the fastener until the detent features 830on the head align substantially with the protrusions 770 on the arms750, at which point the user releases the force on the arms 750, whichmove inward so as to permit the protrusions 770 to mate with the detentfeatures 830. To release the fastener 800 from the multipurpose tool700, the user applies a force to slightly spread the arms 750 so thatthe protrusions 770 disengage the detent features 830. The user may thenseparate the multipurpose tool from the fastener. In other embodiments,the head may include additional notches and/or grooves that permit thehead of the fastener to be “snap-fit”into the distal end of themultipurpose tool. FIG. 17 illustrates the fastener 800 in place withinthe arms 750 of the multipurpose tool 700. Although FIG. 17 illustratesthe multipurpose tool 700 engaging a fastener 800, it is contemplatedthat the multipurpose tool 700 can be used to engage other devices,components, and/or tools.

The inner diameter of the bore 740 formed within the multipurpose tool700 may be selected to be approximately the same diameter as the head820 of the fastener 800. In some embodiments the inner diameter isslightly larger than the diameter of the head of the fastener, while inother embodiments the inner diameter is slightly smaller. In oneembodiment, the inner diameter of the multipurpose tool is about half aninch, and the outer diameter of the multipurpose tool is approximately0.6 inches. In a further embodiment, the inner diameter is approximately0.527 inches, and the outer diameter is approximately 0.625 inches. Thelength of the multipurpose tool 700 depends in part upon the depth ofthe target location below the skin of the patient. For example, thelength of the tool is selected so that the proximal end 720 of the toolextends above the skin of the patient when the distal end 730 of thetool is adjacent the target location. In various embodiments, the lengthof the multipurpose tool 700 is in a range from about 2 inches to about5 inches, although other lengths can be used.

FIG. 18 schematically illustrates an optional retaining clip 950 thatmay be used with the multipurpose tool 700. The retaining clip 950comprises an elongated body having a “C”-shaped clip portion 960 at adistal end and a handle portion 970 at a proximal end. The elongatedbody and the “C”-shaped clip 960 may be configured to slidably engagethe multipurpose tool 700. In some embodiments, the clip portion 960 hasan inner diameter that is slightly larger than the outer diameter of themultipurpose tool so that the clip portion 960 can be pushed onto theproximal (or distal) end of the tool. The circumferential extent and thelength of the “C”-shaped clip portion 960 are large enough to providesuitable frictional coupling to hold the retaining clip in place on thetool. The cross sectional shape of the clip portion 960 and theelongated body may be selected to conform to the cross-sectional shapeof the multipurpose tool 700 to provide a suitably secure engagementtherebetween. In some embodiments, this cross sectional shape issubstantially circular, which permits the retaining clip to be rotatedinto any desired orientation around the longitudinal axis of themultipurpose tool. In the embodiment shown in FIG. 18, the handleportion 970 of the retaining clip 950 comprises a tab 980 that is offsetfrom, and may be substantially orthogonal to the elongated body andwhich can be used to push or to pull the retaining clip 950 into adesired position along and around the multipurpose tool 700. Theretaining clip 950 may be fabricated from a substantially rigid anddurable material such as a metal or a plastic. In some embodiments theretaining clip 950 is formed from stainless steel or titanium.

FIG. 17 schematically illustrates the multipurpose tool 700 engaged withthe retaining clip 950 and fastener 800. The retaining clip 950 has beenpushed toward the distal end of the tool such that the “C”-shaped clipportion is near the distal end of the tool 700. The retaining clip 950can be used to secure the arms 750 of the multipurpose tool 700 aroundthe fastener 800 to be delivered to a target location. Use of the clip950 beneficially reduces the possibility that the arms of themultipurpose tool 700 will spread apart as the tool is delivered to thetarget location through a path between the skin and the spine.Additionally, use of the clip 950 reduces the possibility that thefastener 800 will be dislodged from between the arms as it is advancedalong a percutaneous path. In some procedures, after the fastener 800has been delivered to the target location, the retaining clip 950 can beslid upward toward the proximal end of the tool 700 so as to permit thearms to release the fastener. In certain procedures, the retaining clip950 is completely disengaged from the multipurpose tool 700 after thefastener is delivered to the target location.

The retaining clip 950 provides additional benefits. In certain fixationprocedures, a portion of a fixation element (e.g., a fixation rod) isdisposed within the head of a fastener 800 (e.g., within the “U”-shapedopening shown in FIG. 15) and then secured into position (e.g., with acap screw 900). In some of these procedures, after the fixation elementhas been delivered adjacent the head of the fastener (e.g., generallynear or between the flanges defining the opening), the retaining clip950 advantageously can be used to push the fixation element toward thedistal portion of the “U”-shaped opening and to assist seating it in thehead. Additionally, the retaining clip can hold the fixation element inplace while the cap screw is tightened.

FIGS. 13 and 18 schematically illustrates the proximal end 720 of themultipurpose tool 700 and the distal end of the retaining clip 950(e.g., the “C”-shaped clip portion). In some embodiments, thecircumferential extent of the “C”-shaped clip portion 960 issufficiently large that it slides onto the proximal end 720 of the tool700. However, in other embodiments, the circumferential extent of the“C”-shaped clip portion is smaller, which permits the retaining clip tobe clipped or snapped onto the tool. In other embodiments, the retainingclip and/or the multipurpose tool include a locking feature configuredto prevent the retaining clip from sliding when the locking feature isactivated. In some embodiments, the locking feature comprises one ormore detents that permit the retaining clip to be locked in selectedlocations.

In some procedures, to secure a fastener to a target location in thespine, an instrument such as a screwdriver is used to apply a torquingor twisting force to, for example, the shaft 810 of the fastener 800. Itmay be beneficial to reduce transfer of the twisting force to otherdevices or locations including, for example, the multipurpose tool,adjacent vertebral bodies, surrounding tissue, etc. In some procedures,transfer of the twisting force is reduced by applying a counter-torqueto the multipurpose tool. FIG. 19 is a perspective view of an embodimentof an anti-torque handle 1000 that can advantageously be used secure themultipurpose tool 700 while a fastener 800 is being tightened. Theanti-torque handle 1000 comprises a pair of elongated arms 1010extending axially away from a central ring portion 1020 configured toengage the proximal end 720 of the multipurpose tool 700. The elongatedarms 1010 are sufficiently long so as to enable a surgeon to apply asufficient counter-torque while tightening the fastener 800. In theembodiment shown in FIG. 19, the central ring portion 1020 has an innersurface that defines a central passage that has a size and shapeselected to permit the proximal end 720 of the multipurpose tool 700 topass therethrough. The anti-torque handle 1000 is adapted to reducerelative rotation between the handle and the multipurpose tool after thehandle engages the tool. For example, in some embodiments, the outersurface of the proximal end of the multipurpose tool and the innersurface of the anti-torque handle are configured with correspondinglyshaped surfaces that minimize relative rotation. In the embodiment shownin FIG. 19, these surfaces comprise facets 1030 on the inner surface ofthe central ring portion 1020 of the anti-torque handle 1000 that engagecorresponding facets 780 on the proximal end 720 of the multipurposetool 700 when the handle is placed onto the proximal end of the tool. Inother embodiments, a different number of facets can be used. Forexample, in certain embodiments the proximal end of the tool and theinner surface of the handle are hex-shaped. The facets have alongitudinal extent that can be selected so that the anti-torque handlecan be disposed at a suitable position along the multipurpose tool. Theanti-torque handle can slide along the tool until the lower portion ofthe handle engages the lower portion of the facet, which forms a ledgeto support the handle. In other embodiments, the handle can be securedto the tool using other mechanisms such as, for example, via one or moredetents, clips, tongue-and-grooves, etc.

The anti-torque handle may provide additional advantages to thosedescribed above. For example, it can be disposed on the multipurposetool and used to move, rotate, advance, and/or orient the multipurposetool. In some procedures, the anti-torque handle is grasped by thesurgeon and used to advance the multipurpose tool through thepercutaneous tissue path to target location.

FIG. 20 is a perspective view that schematically illustrates anembodiment of a compression/distraction link assembly 1100 configured toreceive the proximal ends of two adjacent multipurpose tools 700. FIG.21 is a view that schematically shows the link assembly 1100 disposed onthe proximal ends of two adjacent multipurpose tools 700. Thecompression/distraction link assembly 1100 generally comprises twoelongated bodies 1110 that are pivotally coupled about a pivot joint1120. The elongated bodies 1110 have a proximal and distal end, and insome embodiments, the elongated bodies are generally cylindrical inshape. The elongated bodies may have any suitable length including, forexample, about 1 inch. Each of the elongated bodies has an inner surfacethat defines a passage therethrough. The inner diameter of the passageis generally slightly greater than the outer diameter of the proximalend of the multipurpose tool. The inner surface may include one or morefacets 1130 configured to engage with facets 780 on the proximal end ofthe multipurpose tool 700. In certain embodiments two opposing facetsare used; however, other numbers of facets can be used (e.g., six facetsin a hex configuration). In some embodiments the facets 1130 extend theentire length of the elongated bodies 1110, which enables either theproximal or the distal end of the elongated body 1110 to be disposedonto the multipurpose tool 700. The pivot joint 1120 may comprise a pinjoint that permits rotational motion about an axis through the pin. Inother embodiments, a pin-in-slot joint may be used to additionallyprovide limited translation motion between the elongated bodies.

The compression/distraction link assembly 1100 can be used with twomultipurpose tools 700 to compress or distract adjacent vertebral bodiesin the cephcaudal direction during, for example, a fixation or fusionprocedure. By applying suitable forces to one or both of themultipurpose tools, the tools can pivot around the pivot joint such thatthe distal ends of the tools can be moved toward each other (forcompression) or away from each other (for distraction). FIG. 21 is aperspective view that schematically illustrates an example position ofthe tools 700 in a distraction procedure. In some procedures, to pivotone (or both) tools 700, an instrument can be inserted into thepassageway within one (or both) of the elongated bodies 1110 of the linkassembly 1100, and a suitable pivoting force can be applied. In certainprocedures, a multipurpose tool 700 can be used as the instrument, e.g.,the cylindrical portion of the proximal end of the tool 700 can beinserted into the link assembly 1100 and a pivoting force can be appliedto the opposing end of the tool 700. However, any other suitableelongated instrument can be used including, for example, a dilator orobturator.

FIGS. 22 and 23 are plan views that schematically illustrate anotherembodiment of the compression/distraction link assembly 1101. In thisembodiment, the length of the elongated bodies 1111 is greater than inthe embodiment shown in FIG. 20. In some embodiments, the length of theelongated bodies 1111 is in a range from 1 inch to about 8 inches. Inone embodiment, the length is about 6 inches. FIG. 22 schematicallyillustrates how the link assembly can be used in a compressionprocedure. A force F can be applied so as to push the elongated bodies1111 of the link assembly 1101 together. The elongated bodies pivotabout the pivot joint 1121 (which is disposed proximal to the surgeon),causing the distal ends 730 of the multipurpose tools 700 to move towardeach other. Accordingly, fasteners 800 inserted in vertebral bodies willcause the bodies to shift toward each other. Although the force F isshown as applied to the link assembly 1101, the force F may additionallyand/or optionally be applied at any suitable position distal to thepivot joint. In some procedures, a surgeon applies the force F bysqueezing together the elongated bodies 1111 of the link assembly. Theforce F can be applied to shift the vertebral bodies into suitablepositions before securing a fixation assembly (e.g., before tighteningcap screws onto fixation rods).

FIG. 23 schematically illustrates how the link assembly 1101 can be usedin a distraction procedure. In this procedure, the link assembly 1101 isoriented so that the pivot joint 1121 is disposed distal to the surgeonand adjacent the proximal ends 720 of the multipurpose tools 700. Insome embodiments, the link assembly 1101 shown in FIG. 22 is inverted sothat its opposite end is disposed on the multipurpose tools, as shown inFIG. 23. As shown in FIG. 23, when a force F is applied proximal to thepivot joint, e.g., by squeezing the elongated bodies 1111 of the linkassembly together, the distal ends of the multipurpose tools move apart.Accordingly, the fasteners cause a distraction of the vertebral bodiesin which the fasteners are seated.

The embodiment of the link assembly shown in FIGS. 22 and 23advantageously can be used in either a distraction or a compressionprocedure. The link assembly beneficially provides ease of use, becausein both procedures, the surgeon need only apply a squeezing force ofsuitable magnitude to accomplish the desired compression or distraction.In certain embodiments, the link assembly includes a locking featurethat holds the link assembly in a suitable compression or distractionposition after the force F is removed. In some embodiments the lockingfeature comprises a locking element having a pair of generally“C”-shaped clips that clip or snap on to each of the elongated bodies ofthe link assembly to hold them in a desired orientation. In otherembodiments, the locking feature comprises a tether.

FIGS. 24 and 25 schematically illustrate certain acts that may beperformed during various embodiments of procedures used to treat thespine of a patient. FIG. 24 shows a multipurpose tool 700 that has beeninserted into a percutaneous path or entry between the skin S and atarget location adjacent a vertebral body. In some procedures themultipurpose tool is inserted over a dilator or through an accessdevice, which may subsequently be removed. The multipurpose toolgenerally is used to deliver a fastener to the target location. Aninstrument, such as a hex tool or screwdriver, can be inserted into thecentral bore 740 defined by the arms of the multipurpose tool. Theinstrument can be used, for example, to screw the fastener into the boneat the target location. FIG. 24 also shows a guidewire 2000 insertedinto an adjacent percutaneous path to an adjacent target site. A surgeonmay use the instrument, for example, to advance the fastener into thevertebral body. One hand of the surgeon applies a counter-torque to themultipurpose tool by, for example, firmly grasping an anti-torque handledisposed on the proximal end of the tool.

At a later stage of the procedure, the guidewire is removed and a secondmultipurpose tool is inserted into the adjacent opening to deliver afastener to the adjacent target location. An instrument, such as a hextool or screwdriver, is inserted into the second multipurpose tool inpreparation for tightening the fastener. An anti-torque handle may bedisposed on the second multipurpose tool. An instrument such as anendoscopic screwdriver may be used to advance a clamping member (e.g., acap screw) through the multipurpose tool to the head of the fastenerdisposed at the distal end of the tool. It is understood that additionaland/or different acts can be performed in different procedures and thatnot all the illustrated acts are performed in all procedures. Forexample, in some procedures a target location is prepared by forming athreaded opening with a bone probe and/or bone tap. Hardware components,such as a fixation or fusion element, may be delivered to the targetlocation through, for example, a percutaneous path and/or otherincisions. In certain procedures, an access device may be used duringcertain acts of the procedure. Many variations are possible.

In certain procedures, one or more multipurpose tools can be used toassist installing fasteners (such as pedicle screws) and fixationelements (such as fixation rods) at target locations on the spine. Incertain such procedures, the multipurpose tool advantageously providesguidance in delivering the fastener and/or the fixation element to thetarget location. As an example of the some of the advantages provided bya multipurpose tool, an embodiment of one percutaneous fixationprocedure will now be described.

Under fluoroscopy, a trocar and needle (such as a Jamshidi targetingneedle or a bone biopsy needle) are percutaneously passed through theskin and tissue of the patient to a target location on the spine of thepatient (e.g., a pedicle). A guidewire is inserted through the Jamshiditargeting needle and advanced to the target location. Using 30fluoroscopy, a distal end of the guidewire is tamped into the vertebralbody. These acts may be repeated for as many target sites as desired.Short incisions are made on opposite sides of the guidewire to assistdilation of the percutaneous path. The incisions are generally alignedwith each other and may be about 5 mm in length. The percutaneous pathis dilated by inserting a series of one or more dilators. The path maybe dilated until a 40-mm diameter dilator has been used. The smallerdilators can be removed leaving the 40-mm diameter dilator and theguidewire in the percutaneous path. A cannulated tap is threaded overthe guidewire and advanced to the target location. The tap can be usedto tap the target location (e.g., to create a threaded hole in, forexample, the pedicle). Fluoroscopy can be used to assist tapping thetarget location. After tapping is complete, the dilator and the tap canbe removed, leaving the guide wire in the percutaneous path.

A cannulated fastener (e.g., a cannulated pedicle screw) is engaged atthe distal end of a multipurpose tool. The guidewire is threaded throughthe cannulated fastener and the bore defined within the multipurposetool. An instrument such as a hex wrench (e.g., a cannulated 3.5-mm hexwrench) can be used to assist threading the guidewire through thefastener. The distal end of the multipurpose tool is advanced throughthe percutaneous path to the target location. The distal end of a firstmultipurpose tool and a first fastener are disposed at the firstvertebral site. The second guidewire is disposed at the second site.Under fluoroscopy, the fastener can be screwed into the bone at thetarget location using the hex wrench. The multipurpose tool is rotatedso that the slots between the arms of the tool are aligned with anadjacent guidewire (or adjacent multipurpose tool). The anti-torquehandle can be used to rotate the multipurpose tool. The above acts maybe repeated so as to attach as many fasteners to target locations asdesired.

A fixation element, such as a fixation rod, is delivered to the targetlocation. For example, a rod holder can be used to grasp the rod andadvance it to the spine. In some procedures, an additional incision thatextends between the skin and the spine is made between adjacent sites toprovide an access plane through the skin and tissue to the vertebralsites. In other procedures, a tissue tunnel or canal is formed betweenthe target sites as further described below. Using fluoroscopy thefixation element is advanced through the multipurpose tool (and/orvarious incisions or canals) to the target site and positioned asneeded, for example, between the first and second multipurpose tools.The fixation element is then secured to the fasteners, for example, byinstalling cap screws. In certain procedures, a 4.0-mm hex wrench isused to deliver the cap screw through the multipurpose tool and totighten the cap screw to secure the fixation element into position atthe target location. In one embodiment, a hex wrench is used fortightening the cap screw into the first fastener. A rod holder or othergrasper apparatus is used for grasping the fixation rod between the twomultipurpose tools to prevent twisting of the fixation rod as the capscrew is tightened. These acts are repeated as needed to secure one ormore fixation elements to the spine of the patient. After the fixationrod is secured to the fasteners, the multipurpose tools are removed fromthe patient's body. Cap screws are then inserted into the heads of thefirst and the second fasteners and the fixation rod firmly securedtherebetween. In other procedures, similar acts can be used to installadditional fixation and/or fusion elements at vertebral sites.Additionally, similar acts can be used for multi-level procedures andfor procedures at different vertebral sites such as, for example, facetjoints and transverse or spinous processes.

FIGS. 24-25 show various stages of an example spinal procedure, such asa fixation or stabilization procedure. The example procedure shown inFIGS. 24-25 is a one-level procedure, but the acts and stages shown canalso be applied to multi-level procedures. FIGS. 24-25 are intended toillustrate various stages of an example procedure but are not intendedto be limiting with respect to the types of acts, methods, devices, andcomponents that can be used.

First and second guidewires are percutaneously advanced through firstand second percutaneous paths to a first and a second target location onthe spine of the patient. In the view shown in FIG. 24, first and secondguidewires 2000 have been inserted at first and second target locations,and a first multipurpose tool 700 has been inserted over the guidewireand advanced to the first target location. A cannulated instrument canthen be disposed within the bore 740 defined within the multipurposetool 700. When in use the cannulated instrument may have a handle thatextends above the multipurpose tool. The instrument can be a hex wrenchor a screwdriver configured to screw a fastener into the bone at thefirst vertebral site. FIG. 24 shows the surgical site after thecannulated instrument has been removed from the first multipurpose tool.

A series of dilators may then be used to expand the diameter of thesecond percutaneous path. In one procedure, three nested, cannulateddilators are used; however, a different number can be used in otherprocedures. The outermost dilator has an outer diameter of about ½ inch,and the outer diameter of the first multipurpose tool is about ¾ of aninch. In this procedure, the centers of the two adjacent percutaneouspaths are spaced about 1.5 inches apart.

The dilators at the second site are then removed and an instrument suchas, for example, a bone probe or a bone tap is advanced to the secondvertebral site. The bone probe and/or bone tap can be used, for example,to form a threaded hole in the bone (e.g., in a pedicle). The instrument(e.g., the bone probe/tap) is then removed. As shown in FIG. 25, acannulated fastener 800 (e.g., a cannulated pedicle screw) is disposedbetween the arms of a second multipurpose tool 700, and the fastener 800is threaded over the guidewire 2000 in preparation for insertion intothe second percutaneous path. A retaining clip 950 is attached to thesecond multipurpose tool 700 and is then slid toward the distal end ofthe tool to secure the fastener and to prevent the arms of the tool fromspreading apart. In a subsequent stage of the procedure, the secondmultipurpose tool is advanced to the second vertebral site, the secondguidewire is removed, and an instrument such as a hex wrench orscrewdriver is inserted through the bore of the second tool to screw thesecond fastener into the bone at the second target location. At thisstage of the procedure, the retaining clips on both multipurpose toolsare retracted (e.g., pulled away from the spine).

In one embodiment, an incision is made between the two multipurposetools, which extends from the skin to the target sites adjacent thespine. The incision is used to provide an access plane through which afixation element (e.g., a fixation rod) can be advanced to the targetsite by, for example, a grasper apparatus. The fixation rod ismanipulated by a grasper apparatus until each end of the rod is disposedwithin the heads of the first and second fasteners. As further describedherein, the retaining clips can be slid downward (e.g., toward thespine) to assist in pushing and/or holding the ends of the fixation rodin place within the heads. A first cap screw is then advanced into thebore in the first multipurpose tool by an instrument such as a hexwrench. The surgeon tightens the first cap screw so as to secure the endof the rod at the first vertebral site. In some procedures, acompression or distraction procedure can be performed to shift thevertebrae into suitable positions. After the second cap screw istightened, both multipurpose tools are removed.

In some methods, a tissue tunnel (or canal) is formed between adjacenttarget vertebral sites to facilitate positioning a fixation element(e.g., a fixation rod) between the target sites. FIG. 26 schematicallyillustrates a tissue tunnel 3000 formed between adjacent heads offasteners 800. In certain procedures, the tissue tunnel 3000 is formedwith a pointed passageway tool 3100 as schematically illustrated in FIG.27 (in which the multipurpose tools are not drawn for purposes ofclarity). In certain embodiments, the passageway tool 3100 has a pointedtip 3110 that can be used 10 percutaneously to pierce the tissue of thepatient so as to create the tissue tunnel 3000. FIGS. 28 and 29schematically illustrate an embodiment of a passageway tool 3100comprising a needle attached to a handle. The needle has a distal endwith a pointed tip 3110 for puncturing tissue.

In certain procedures, the tip of the passageway tool is advanced to thetarget location by inserting the tip of the tool into the central borewithin the multipurpose tool. The passageway tool is inserted into thebore through the slots between the arms of the multipurpose tool so asto permit a wider vertical range of motion of the passageway tool. Whenthe tip of the passageway tool reaches the target location (e.g.,adjacent the head of a fastener), the passageway tool is pushed towardan adjacent target location. The pointed end of the passageway toolthereby creates the tissue tunnel as it slides or otherwise movesbetween adjacent target locations. In some procedures, the passagewaytool is inserted into one of the percutaneous paths and used to make acomplete tissue tunnel from one target site to an adjacent target site.However, in other procedures, the passageway tool is used to make afirst tunnel extending partially toward the adjacent site. Thepassageway tool is then inserted into the adjacent percutaneous path andmanipulated to make a second tunnel that joins with the first tunnelthereby forming the complete tissue tunnel. In yet other procedures, two(or more) passageway tools are used to create the tissue tunnel.

An advantage of using the passageway tool to create the tissue tunnel isthat no additional punctures, incisions, or percutaneous paths in thepatient are required. Because the passageway tool is advanced andmanipulated through a previously opened percutaneous path, additionaltrauma to the patient is reduced. In order to form a more horizontaltissue tunnel (e.g., substantially parallel to an axis between theadjacent vertebral sites), a proximal end of the passageway tool (e.g.,the handle which is outside the patient) can be lowered toward thepatient's skin thereby causing the distal end of the tool to assume amore horizontal orientation. As the passageway tool is manipulated tocreate the tissue tunnel, surrounding tissue at the sides of thepercutaneous path may be stretched or retracted. However, a suitablycurved or shaped needle on the passageway tool can permit easier entryto the target location and can reduce trauma to surrounding tissue asthe tool is manipulated to form the tissue tunnel.

FIGS. 28 and 29 are perspective views that schematically illustrate anembodiment of a passageway tool 3100 comprising a needle 3200 attachedto a handle 3300. The needle 3200 has a distal end with a sufficientlysharp tip 3110 for puncturing tissue. In some embodiments, the needle isshaped so that a sufficiently horizontal tissue tunnel can be formed.For example, the needle may have a curved “C” or “S” shape in someembodiments. In the embodiment shown in FIGS. 28 and 29, the needlecomprises three linear segments: a tip segment, a middle segment, and ahandle segment. An angle θ is defined between the tip segment and themiddle segment. The lengths of the segments and the angle θ can beselected to permit the passageway tool to rotated, oriented, andotherwise manipulated within the percutaneous path to provide asufficiently horizontal tissue tunnel while minimizing trauma to thesurrounding tissue. FIG. 29 shows example dimensions (in inches) of oneembodiment of the passageway tool that is configured for insertion intoa percutaneous opening with an inside diameter of about 0.6 inches. Inthis embodiment the tip segment (a) is 1.0 inches, the middle segment(b) is 2.1 inches, the handle segment (c) is about 3.5 inches, and theangle θ is about 125 degrees. Other embodiments of the passageway toolcan have different dimensions and configurations, and the abovedimensions and angles are intended to be representative and notlimiting.

The following list describes various acts that may be performed in oneembodiment of a percutaneous fixation procedure utilizing themultipurpose tool and the passageway tool.

-   1. Under fluoroscopy, locate a target site (e.g., a pedicle) of the    vertebral body with a Jamshidi targeting needle (or a bone biopsy    needle).-   2. After locating the target site, use fluoroscopy to determine if    the target site is suitable for tapping. If the site is suitable,    tamp the Jamshidi targeting needle into the site.-   3. Remove the stylet from the Jamshidi targeting needle, and thread    a guidewire through the Jamshidi targeting needle. Tamp the    guidewire into the vertebral body under fluoroscopy.-   4. Repeat steps 1, 2, and 3 as needed to prepare additional target    sites for a guidewire.-   5. Make an incision on either side of each guidewire as if drawing a    line through the guide wires. The incisions may be about 5 mm in    length.-   6. Dilate over the guide wire until a 15-mm diameter dilator has    been used.-   7. Remove the smaller dilators leaving in place the 15-mm diameter    dilator and the guidewire.-   8. Thread the guidewire thru a cannulated tap and tap the target    site (e.g., the pedicle) using fluoroscopy for guidance.-   9. After tapping is complete, the dilator and the cannulated tap are    removed, while the guidewire is left in place.-   10. Attach a fastener (e.g., a pedicle screw) to a distal end of a    multipurpose tool. Thread the guidewire thru the multipurpose    toot/fastener assembly using a cannulated 3.5-mm hex wrench. A    retaining clip may be used to hold the fastener in place and to    prevent the arms of the multipurpose tool from spreading apart    during insertion.-   11. Under fluoroscopy, advance the multipurpose tool/fastener    assembly to the target site. An anti-torque handle can be disposed    on the proximal end of the multipurpose tool to assist in advancing    the tool. Using a screwdriver or a hex wrench, screw the fastener    into the bone at the target site. Remove the guidewire after the    fastener is secured to the target site. Rotate the multipurpose tool    so that one of the slots between the arms of the tool is    sufficiently aligned with the adjacent guidewire or multipurpose    tool. The anti-torque handle can be used to rotate the multipurpose    tool.-   12. Repeat steps 6 through 11 as needed.-   13. Form a tissue channel between two adjacent vertebral sites using    a pointed passageway tool. Insert the passageway tool into the    multipurpose tool disposed at either site until the point of the    passageway tool reaches the head of the fastener. The passageway    tool is then advanced toward the other vertebral site so that a    “tunnel” is created between the two heads of the fasteners. The    passageway tool may have a curved or shaped needle portion that can    be rotated and oriented so as to form a tissue tunnel substantially    parallel to the cephcaudal direction. Using fluoroscopy, verify that    a suitable “tunnel” has been formed.-   14. Retract the retaining clip from each of the multipurpose    tool/fastener assemblies so that the distal end of the retaining    clip is above the “tunnel”. Verify with fluoroscopy.-   15. With an axial fixation rod holder, grasp one end of the fixation    rod and place the other end through the multipurpose tool. Advance    the rod until each end of the rod is over a respective head of a    fastener. Verify with fluoroscopy.-   16. When the rod placement is verified, push down each of the    retaining clips to secure the ends of the fixation rod onto the    heads of the fasteners.-   17. With the fixation rod in position, advance cap screws through    the bore in the multipurpose tool using a 4.0-mm hex wrench. One cap    screw may be loosely tightened to permit an end of the rod to move.    The other cap screw should be tightened to specification with the    4.0 mm hex wrench to secure the fixation rod.-   18. If compression/distraction of the vertebral bodies is desired,    the compression/distraction link assembly is disposed onto the    proximal ends of the two multipurpose tools.-   19. Compress or distract as needed for the fixation procedure using    the compression/distraction link assembly.-   20. When the vertebral bodies are in the desired positions, torque    down the loosely secured cap screw onto the fixation rod using the    4.0-mm hex wrench.-   21. After the fixation rod is secured, remove the retaining clips    from the multipurpose tools and then remove the multipurpose tools    from the percutaneous entry path.

In other embodiments of this procedure, additional and/or different actsmay be performed, and some or all of the acts may be performed in adifferent order. Variations of the above embodiment may be used formulti-level spinal procedures. Further, variations of the aboveprocedure can be adapted for use where the target site is a facet joint,a transverse or spinous process, or other suitable vertebral location.Many variations are possible.

C. Additional Methods and Devices for Providing Access to a SurgicalSite As described above, in various procedures a passageway tool is usedto create a tissue tunnel or canal between the adjacent target sites, afixation element (e.g., a fixation rod) may be advanced through thecentral bore of the multipurpose tool and into the tissue tunnel formedby the passageway tool. It is advantageous if the fixation element isinserted into the multipurpose tool through the slots defined betweenthe arms of the tool so as to provide a wider vertical range throughwhich to manipulate the element. FIG. 30 schematically illustrates thetunnel 3000 formed by the passageway tool and the fixation rod 140 beingadvanced into position. FIG. 31 schematically illustrates an initial anda final position of the fixation rod 140. In manipulating the rod intoposition, portions of the tissue surrounding the percutaneous path maybe stretched and/or retracted; however, additional incisions, punctures,or percutaneous paths are generally not required in order to positionthe fixation element within the tunnel.

In some procedures, the fixation rod is pushed through the tissuetunnel, and in other methods the rod is pulled through the tissuetunnel. In yet other embodiments, a combination of pushing and pullingis used. FIG. 32 schematically illustrates a “pushing” method that usesa force F to push the fixation rod 140 into position. In FIG. 32, therod 140 is pushed from right to left as indicated by the arrow (“roddirection”). In some pushing techniques, no special tools are used, andthe fixation rod can be pushed by any suitable device including, forexample, a hex tool or a screwdriver. The rod is manipulated into thetissue tunnel 3000 as it is being pushed, because of the absence ofresistance from the surrounding tissue. The movement of the rod in thetunnel may be lubricated by blood present in the tunnel.

FIG. 33 schematically illustrates a “pulling” technique that can be usedalone or in combination with the pushing technique. In this embodimentof the pulling technique, a threading feature and/or flexible pullermember, such as, for example, a suture, a cable, or a wire 176 isconnected to an end of the fixation rod 140, and a force F is applied toan end of the threading feature so as to pull the rod through thepassageway 3000 created by the passageway tool. In some techniques, thesuture is connected to the fixation rod by an attachment element 178.The attachment element 178 may comprise an eyelet or a finger trapsuture or flexible cap or some other suitable device or structure forconnecting the suture 176 to the rod 140.

Some techniques utilize a combination of the pulling and the pushingmethods. As shown in FIG. 34, a coupling element 165 may be used tomechanically connect a pushing device 160 (such as a hex tool, ascrewdriver, or other instrument) to the fixation rod 140 while it isbeing advanced into position. The coupling element 165 may aid intransmitting the pushing force to the fixation rod. The coupling element165 may also stabilize the pushing motion by inhibiting lateraldeflection of the rod away from the direction of the passageway andcanal created by the passageway tool. The fixation rod may also bepulled while it is being pushed. In certain techniques, pulling forceand pushing force are alternated. FIG. 35 schematically shows dimensionsand sizes for one embodiment of a multipurpose tool 700 that can be usedwith various methods discussed herein. The multipurpose tool 700 shownin FIG. 35 has an inner diameter (I.D.) of 0.527 inches, an outerdiameter (O.D.) of 0.625 inches, and an inserted depth between the skinS and the distal portion of the rod-receiving opening in the fastenerhead of 1.5 inches.

FIGS. 36A-39 schematically illustrate further devices and methods thatcan be used to provide surgical access to a vertebral site. FIGS. 36A,36B, and 37 schematically illustrates a pair of elongated, generally“U”-shaped (or hemispherical) pedicle screw installation tools 4000. The“U”-shaped tool has an inner channel 4010 that is sized to provideclearance for a pedicle screw assembly 800 and a fixation rod 140. Insome methods, two installation tools are inserted through the skin ofthe patient and extend from the skin to the vertebral site. Apositioning member 4020 can be secured to both installation tools 4000so as to preserve the position and orientation of the installation toolsand to prevent the tools from moving towards or away from each other. Inone embodiment, one positioning member is secured to each side of thepair of installation tools, as shown in FIG. 36A, a top view. In otherembodiments, a single positioning member is used, as shown in FIG. 37.In certain embodiments, the positioning member comprises a pivot strap4022 that is attached to the installation tools via screws or rivets4024. In some embodiments, one or more of the “U”-shaped installationtools have a side window 4015 (e.g. “channels” and/or “cut outs” or“mating openings” and/or “laterally facing openings”) disposed at thedistal end. The side window 4015 is configured to receive the fixationrod 140.

FIG. 36B is a cross-section taken through line B-B in FIG. 36A, and alsoschematically shows an embodiment of a hex screwdriver 4030 that can beused to guide the pedicle screws 800 through the channel 4010 betweenthe arms of the “U.” Additionally, the hex screwdriver 4030 can be usedfor angular alignment and adjustment. In some embodiments, the hexscrewdriver 4030 comprises a ball feature 4032 disposed on the shaft ofthe screwdriver 4030. In such embodiments, the screwdriver has a rangeof transverse angular motion. However, in other embodiments, two ballfeatures 4032 are disposed on the shaft. When both ball features aredisposed within the “U”-shaped channel, the transverse angular motion ofthe screwdriver is substantially limited, and the screwdriver provideslinear (e.g., vertical) movement (as well as rotational movement).

FIG. 38 shows two pedicle screw installation tools 4000 inserted atadjacent vertebral sites. A distal end of each of the tools can includeone or more side windows 4015, which can be used to assist positioningof a fixation member. Pedicle screws 800 can be inserted into thepedicle via a targeting needle and a guidewire (as described above).

In one technique, an incision is made between the two installation toolsand the fixation element (e.g., a rod) is inserted through the incisionand into position onto the pedicle screws. After the fixation element isin position, the element can be secured to the pedicle screws via setscrews or cap screws. The set screws or cap screws can be inserted viathe installation tools (and the guidewire in some methods). In thistechnique, there is generally no debridement of muscle tissue, and deadtissue is absorbed by the body.

D. Systems and Methods for Spinal Procedures Using Break-Off Screw Heads

FIGS. 40-45 schematically illustrate an example spinal procedure for atleast partially percutaneously delivering a fixation element 140 (e.g. afixation rod) to a target site adjacent the vertebrae of a patient. Theprocedure may include, for example, a fixation, a fusion, and/or othersuitable stabilization procedure, and the procedure can be a one-levelor multi-level procedure. The target site may be any suitable site onthe vertebra of the patient including, for example, a pedicle, a spinousor transverse process, a facet joint, or a combination of such sites.Although a generally posterior approach is illustrated in FIGS. 40-45(e.g., a postero-lateral approach), in other procedures other spinalapproaches may be used such as, for example, anterior, lateral, orretroperitoneal.

FIG. 40 is a perspective view that schematically illustrates a stage inthe procedure when two guidewires 2000 have been delivered to suitabletarget sites. For example, a trocar and needle (such as a Jamshidineedle or bone biopsy needle) are percutaneously passed through the skinS and into the targeted pedicle and into the vertebral body V. Thetrocar and needle form a percutaneous access path that is sometimesreferred to herein as a tissue tunnel. In one technique, the trocar isinserted into the needle and the trocar and needle are advanced togetherthrough the skin at a skin puncture location and through subcutaneoustissue (e.g., through fat, muscle, and fascia) until a distal end of thetrocar and needle are at the vertebral target site. The needle andtrocar thus create a tissue tunnel through subcutaneous tissue. In onemethod, a generally posterolateral approach is employed and the initialadvancement of the needle and trocar positions the needle and trocar atthe pedicle of the target vertebra. Advancement of the needle and trocarmay be aided by fluoroscopy, e.g., using a C-arm or other similartechnique.

After a percutaneous entry, or percutaneous entry path, has been createdthrough the skin and subcutaneous tissue, the vertebral target site maybe prepared, if desired. In one method, the needle and trocar areadvanced further into the target vertebra at the vertebral target siteto form a tunnel in the target vertebra. The tunnel may be formed in thepedicle and is sometimes referred to as a pedicle tunnel. A proximal endof the trocar may remain outside the patient, above the skin puncturelocation throughout the target site preparation. Preparation of thevertebral target site may include further procedures, such as tapping ofthe pedicle tunnel.

In one embodiment, the trocar is removed, leaving the needle in thepedicle. A guidewire 2000, or other elongate body, is inserted into theproximal end of the needle. The guidewire may be advanced through thetissue tunnel and through the pedicle tunnel within the needle. In oneapplication, the guidewire is advanced until a distal end of theguidewire is located in the vertebral body of the target vertebra. Theguidewire extends proximally from the skin and the proximal end of theneedle at the stage of the procedure illustrated in FIG. 40. In sometechniques, the guidewire has an outer diameter of about 1.5 mm. Theneedle is removed leaving the guidewire in place, extending distallyinto the pedicle tunnel and proximally out of the skin. In similarmanner, additional guidewires can be delivered to other target vertebralsites (e.g., FIG. 40 schematically illustrates two guidewires).

In some applications, further dilation of the percutaneous access pathor entry facilitates insertion of an access device and/or retractor 101.In certain techniques, a small incision is created at the skin puncturelocation, which in one technique is about 5-15 mm long. In somevariations, an incision that is less than 5 mm can be created. Theincision also can extend a distance into the tissue beneath the skin.The incision facilitates the insertion of one or more dilators (orobturators) over the guidewire to increase the size of the percutaneousaccess path or entry. In some techniques, a cannulated dilator with anouter diameter of about 5 mm is used. The dilator may be advanced atleast a substantial portion of the distance from the skin puncturelocation to the surface of the vertebra to reduce the resistance of thetissue beneath the skin to the insertion of an implant. The dilators areremoved prior to insertion of a retractor in one technique.

In certain techniques, an access device and/or retractor 101 is placedwithin the percutaneous entry path to provide a space for the insertionof an implant at a later stage of the procedure, as shown in FIG. 41.Additionally, the retractor can protect the tissue from damage caused byinstruments (e.g., sharp cutting flutes of a cannulated tap). Theretractor 101, in certain embodiments, is an elongate body having aproximal end 121 and a distal end 111 and having a bore or cannulation104 extending therebetween. The elongate body has a length such that theproximal end 121 extends out from the skin when the distal end 111 isadjacent the vertebral site. The bore 104 has an inside diameter that isslightly larger than the width of implants to be delivered therethrough.In some embodiments, the elongate body may include one or more slots 102or openings to provide an increased amount of access to the vertebralsites. For example, in some embodiments the elongate body has agenerally “C”-shaped cross section, wherein the opening in the “C”comprises a slot 102 that extends between the proximal 121 and distal111 ends. Certain such embodiments also have a shorter slot or openingat the distal end to provide further access to implants at the targetsite. The proximal end 121 of the retractor may be fashioned into ahex-shape (or other suitable shape) to permit instruments, handles, etc.to grasp and firmly hold the retractor. The outside surface of theretractor may be threaded or ribbed to prevent the retractor frommigrating during the procedure. The retractor may be configured topermit other instruments (e.g., a visualization instrument) to beattached thereto. The retractor is fabricated from a substantially rigidmaterial such as a metal (e.g., stainless steel or titanium). In oneembodiment, the retractor is made from plastic, which advantageously canelectrically insulate body tissue from implants and instruments withinthe bore of the retractor. The retractor can be made of material (suchas plastic or thin metal) which is radiolucent, allowing forfluoroscopic visualization through the retractor.

In some techniques, the retractor is inserted into the dilatedpercutaneous access path and advanced through the tissue tunnel untilthe distal end is adjacent the target site. The retractor 101 may beadvanced over the guidewire 2000 using a cannulated obturator 105 (orcannulated dilator) as schematically illustrated, for example, in FIG.41. Additional retractors can be positioned so as to provide access toadditional target sites. In techniques using “C”-shaped retractors, theopenings in adjacent retractors may be aligned so as to face each other.

Optionally, it may be advantageous to prepare the pedicle tunnel byforming threads within the tunnel. One method of forming threads in thepedicle tunnel involves tapping the pedicle tunnel with a cannulated tap106. A cannulated tap 106 is a low profile instrument that has anelongate body and an outside surface. The elongate body extends betweena proximal end and a distal end. A bore, or cannulation, is formedthrough the elongate body between the proximal and distal ends. Theelongate body has formed thereon a structure 107 configured to forminternal threads within the pedicle tunnel, e.g., on the outer surface.The cannulated tap 106 may be advanced over, e.g., slid over, theguidewire until the distal end is at the vertebral target site. FIG. 41is a cutaway perspective view that schematically illustrates thecannulated tap 106 being advanced over the guidewire 2000 and throughthe bore 104 in a retractor 101. Thereafter the cannulated tap may berotated about the guidewire and advanced, turning the cannulated tapinto the pedicle tunnel. As the cannulated tap advances the threads areformed in the pedicle tunnel. Tapping creates threads in the pedicletunnel that will mate with corresponding threads on an implant to beinserted later.

An implant such as, for example, a fastener (e.g., a pedicle screw) canbe inserted into and advanced to the target location through the bore inthe retractor. In one technique, a fastener such as, for example, acannulated pedicle screw, is inserted over a proximal end of theguidewire. In some procedures, a cannulated screwdriver or otherinstrument can be used to move the fastener through the access device tothe vertebral site, where it can be attached to the pedicle andvertebral body (e.g., by screwing with the cannulated screwdriver). Inone method, after insertion and attachment of the fastener, thescrewdriver and the guidewire can be removed, leaving the fastener andretractor in place.

In certain techniques, the fastener is a screw with an extended breakoffhead. FIGS. 42A and 42B include side views (from two roughlyperpendicular directions) schematically showing an embodiment of a screw801 with an extended breakoff head 821. For example, the fastener maycomprise an elongated screw portion 811 extending along a longitudinalaxis and having threads configured to mate with the threads formed inthe pedicle tunnel by the cannulated tap. The screw portion 811 may becannulated to permit passage over a guidewire. The screw portion 811 ofthe fastener is attached to a breakoff head 821 that, in someembodiments, comprises a housing 823 and an elongated body 825. Thehousing 823 is configured to retain a fixation element 140. For example,the housing 823 may include a portion that is substantially “U”-shapedin a longitudinal cross-section relative to the longitudinal axis,generally similarly to the “U”-shaped head of the fastener describedwith reference to FIG. 15. A portion of a fixation element 140 (e.g., anend of a fixation rod) may be placed within the housing 823 and securedby, for example, a cap screw 900 as further described herein. Thehousing 823 may be configured with facets 828 (such as a hex shape) thatcan couple to other tools such as a screw head cutter (described furtherbelow).

The head 821 of the fastener shown in FIGS. 42A and 42B furthercomprises the breakoff head, which is an elongated body 825 attached tothe housing 823 at a neck 826 and extending to a proximal end 829. Thebreakoff head 821 has a length between the neck 826 and the proximal end829 that is sufficient for the proximal end 829 to extend above the skinof the patient when the fastener is secured to the target site.Advantageously, such a fastener can be advanced to the target site bymanually holding the proximal end and guiding the screw portion throughthe bore of the retractor and into, e.g., the pedicle tunnel. Because ofthe length of the breakoff head, the proximal end of the fastenerremains outside the patient. Accordingly, such a fastener is readilyaccessible to the physician, unlike certain smaller fasteners that canbe difficult to access when placed at the target site at the distal endof the tissue tunnel. In one embodiment, the length of the breakoff headis sufficient for the proximal end to extend above the retractor so thatthe proximal end can be coupled to other instruments.

The breakoff head 821 has an outer surface 827 that may be shaped (e.g.,with a hex shape) to permit such coupling to instruments such as, e.g.,a countertorque handle or removal device. The breakoff head 821 has abore or cannulation 802 extending between the neck 826 and the proximalend 829 to permit passage of the fastener 801 over a guidewire. In oneembodiment, the outer surface 827 of the breakoff head 821 comprises oneor more slots 804 or openings to assist or guide passage of a fixationelement (e.g., a fixation rod) to the target site. In the embodimentshown in FIGS. 42A and 42B, a first slot 804 extends the entire lengthof the outer surface on one side of the breakoff head. Thus, thebreakoff head has a proximal portion that is substantially “C”-shaped ina transverse cross section relative to the longitudinal axis. A secondslot 803 on the opposing side may extend from the neck part way to theproximal end. The first and second slots 803, 804 align with the openingdefined with the arms of the “U”-shaped housing 823 to permit portionsof the fixation element to be positioned within the housing 823.

In some embodiments, the head 821 has an elongated body 825 extendingalong a longitudinal axis and has a distal portion 823 that issubstantially “U”-shaped in a longitudinal cross section relative to thelongitudinal axis. The elongated body 825 has a proximal portion that issubstantially “C”-shaped in a transverse cross section relative to thelongitudinal axis. A first slot 804 is defined in the substantially“C”-shaped proximal portion and a second slot 803 is defined in thesubstantially “U”-shaped distal portion, and the first slot is alignedwith the second slot. The housing 823 includes a portion that issubstantially “U”-shaped in a longitudinal cross-section relative to thelongitudinal axis, and the substantially “U”-shaped distal portion ofthe elongate body 825 is aligned with the substantially “U”-shapedportion of the housing.

The fastener may be fabricated from a substantially rigid material suchas a metal (e.g., stainless steel or titanium). The breakoff head andthe housing generally may be integrally machined from the same material.In some embodiments, the neck is configured so that the breakoff headcan be detached from the housing and then removed from the patient. Forexample, the neck 826 may comprise a region of material having a reducedcross sectional area compared to other regions of the breakoff head.Accordingly, when a differential torque or shearing force is appliedbetween the housing and the breakoff head, the neck will mechanicallyfail (e.g., break, snap, or fracture) when the applied torque orshearing force reaches a sufficiently large value (e.g., a yield stressof the material). In some embodiments, the neck 826 comprises one ormore grooves 805 cut into the outer surface (and/or an inner surface) ofthe breakoff head to provide the reduced cross section suitable for thebreakoff feature of the neck (see detail B in FIG. 42B). However, inother embodiments, the breakoff feature is achieved by, for example,perforating the neck or by any other suitable mechanism that reduces theyield stress at the neck.

FIG. 43 is a perspective cutout view that schematically illustrates astage in the example procedures when two fasteners with extendedbreakoff heads 821 are positioned over guidewires 2000 within adjacentretractors 101. Each fastener is aligned so that the first slot 804 inthe breakoff head 821 aligns with the slot 102 in the “C”-shapedretractor 101. Additionally, the adjacent retractors are aligned so thatthe slots are generally aligned with each other. Accordingly, thealigned slots in adjacent retractors and breakoff heads define guidesfor opposing ends of a fixation element to be advanced to the targetsite as further described below. In some techniques, the guidewires areremoved from the patient after insertion of the fasteners.

In some embodiments, two separate incisions are made and two retractorsare inserted and a fixation element is inserted through one retractor asdiscussed above. In another embodiment, an incision is made between thetwo adjacent retractors, along an imaginary line joining the alignedslots of the retractors. The incision extends below the skin and throughtissue to the adjacent target vertebral sites. The incision creates apercutaneous path for the insertion of a suitable fixation element. Thepercutaneous path is a portion of a plane defined between adjacentretractors and may be referred to herein as a tissue plane.

In some techniques, the fixation element is advanced through the tissueplane with the aid of a grasping instrument. As described above withreference to FIG. 43, the generally aligned slots in the “C”-shapedretractor and breakoff head define a guide for advancing an end of thefastener toward the housing of the fastener at the target site. In onetechnique, opposing ends of the fixation element are placed within theguides formed by opposing retractor/breakoff heads, and the fixationelement is advanced through the tissue plane to the vertebral site. Theguides provide several benefits. For example, the guides assist inkeeping the fixation element in the tissue plane as it is advanced tothe target site and facilitate insertion of the ends of the fixationelement into the housings of the fasteners. Also, the use of guidesmakes it easier to advance the fixation element through the tissueplane, since the portions of the fixation element disposed in the guidesdo not experience resistance from the tissue. FIGS. 44A and 44B includea top view (FIG. 44B) that schematically illustrates the generallyaligned “C”-shaped retractors 101 and breakoff heads 821 and thefixation element 140 (here, a rod) with opposite ends disposed in theguides.

However, in other techniques, only one end of the fixation element isplaced within a guide, and the fixation element is advanced to thetarget site, for example, by advancing the fixation element at an angle.When the fixation element has reached the target sites, the ends of theelement are positioned within the housings of the fasteners and thensecured, e.g., by cap screws. In some techniques, the cap screw isadvanced through the bore of the extended breakoff head to reach thehousing of the fastener. The housing has an inner surface which isthreaded to receive the cap screw. In one embodiment, the threads in thehousing extend into the inner surface of the breakoff head near the neckwhich beneficially permits the cap screw to engage the threads at a moreaccessible, proximal position.

An instrument such as a screwdriver can be used to tighten the capscrews. As schematically illustrated in FIG. 44A, in some techniques, acountertorque handle 600 is attached to the proximal end of the breakoffhead 821 (which extends above the proximal end of the retractor) and isused to provide countertorque while the cap screws are being tightened.In other techniques, an elongated tube having a notch at a distal endconfigured to mate with the fixation element is advanced over thebreakoff head so that countertorque can be applied to the fixationelement. In some techniques, a grasping instrument is used to applycountertorque to the fixation element. If desired, compression and/ordistraction of the vertebrae may be performed prior to the finaltightening of the cap screws.

After the fixation element has been secured, the breakoff heads of thefasteners are detached from the housing and removed from the patient. Insome techniques a screw head cutter and/or removal tool 602 is attachedto the breakoff head, and a differential torque or shearing force isapplied so as to shear (or snap or otherwise break) the breakoff headfrom the housing. FIG. 45 is a perspective view that schematicallyillustrates a stage of the example procedure when the screw head cutter602 has been attached to the breakoff head disposed in the retractor 101on the right side of the drawing in preparation for detachment from thehousing. FIG. 45 also illustrates the retractor 101 on the left side ofthe drawing in which the breakoff head has been removed.

FIG. 46 is a perspective view schematically illustrating a stage in anexample two-level spinal procedure, for example, a two-level fixation orstabilization procedure. At the stage shown, the screw head cutter 602is attached to the breakoff head 821 in the rightmost retractor 101 inpreparation for detachment and removal from the patient. The breakoffhead has been removed from the middle retractor, while the breakoff head821 is still within the leftmost retractor 101 at this stage. Thus it isrecognized that the devices and methods presented herein are suitablefor use in one-level as well as two-level or multi-level spinalprocedures.

FIGS. 47-48 schematically illustrate an embodiment of a screw headcutter 602 which is generally similar to the screw head cutterillustrated in FIGS. 45-46. The screw head cutter 602 is adapted todetach a breakoff head 821 from a housing in a fastener by, for example,exerting a differential torque or shearing force between the breakoffhead 821 and the housing 823. FIG. 47 is a perspective view and FIG. 48is an exploded perspective view.

In the embodiment shown in FIGS. 47-48, the cutter comprises a first 604and second 606 handle, an inner sleeve 608, and an outer sleeve 610. Thefirst and second handles 604, 606 each comprise a central annularportion 612 that can be attached to a proximal end of the inner sleeveand the outer sleeve, respectively. For example, the ends of the sleevesmay comprise a hex shaped portion 614 that is configured to mate withhex-shaped facets 616 on an inner surface of the central annular portion612 of the handles 604, 606 (see FIG. 48). The inner and outer sleevesare each elongated bodies configured so that the inner sleeve can bedisposed within a central cavity in the outer sleeve. For example, theinner and outer sleeves may comprise generally cylindrical tubes withthe outer diameter of the inner sleeve being slightly less than theinner diameter of the central cavity in the outer sleeve so that theinner sleeve can slide into the outer sleeve. The exploded views in FIG.48 illustrate a possible method of assembling the screw head cutter. Thesecond handle 606 is attached to the proximal end of the outer sleeve610, and the inner sleeve 608 is inserted into the central cavity in theouter sleeve 610. The proximal end of the inner sleeve has an enlargedcross section (compared to the elongated tubular portion), whichprevents the inner sleeve from sliding through the outer sleeve andwhich extends above the proximal end of the outer sleeve. The firsthandle 604 is then attached to the proximal end of the inner sleeve 608.The inner sleeve can rotate within the outer sleeve, hence, forcesapplied to one or both handles can be used to turn the inner sleeverelative to the outer sleeve.

The inner sleeve comprises a passageway with a cross-sectional shapethat permits the inner sleeve to slide onto the breakoff head, therebysubstantially surrounding the breakoff head. An inner surface of thepassageway may be configured with facets (e.g., hex cuts) that mate withcorresponding facets (e.g., a hex shape) on the outer surface of thebreakoff head. In some embodiments, the passageway is disposedsubstantially centrally within the inner sleeve. However, in otherembodiments the cross-sectional shape of the passageway resembles thecross-sectional shape of the breakoff head. For example, the passagewaycan be “C”-shaped to accommodate a “C”-shaped breakoff head. When theinner sleeve is slid onto the breakoff head, a portion of the innersleeve is disposed within the central bore of the breakoff head, whichbeneficially can support and stabilize the breakoff head during thedetachment procedure.

The screw head cutter is coupled to a fastener by guiding the cutteronto the breakoff head so that the inner sleeve passes over the breakoffhead (as described above). The outer sleeve may be slightly longer thanthe inner sleeve so that a distal end of the outer sleeve engages thehousing of the fastener. Accordingly, the inner sleeve engages thebreakoff head, and the outer sleeve engages the housing, so that forcesapplied to the first and second handles tend to cause a relativerotation of the inner and outer sleeves. The relative rotation exerts ashear stress on the breakoff head, which as described above, failsmechanically at the neck, thereby detaching the breakoff head from thehousing. In one technique, the second handle is held firmly so as not torotate the housing (which is coupled to the vertebral site by the screwportion). A force is applied to the first handle to cause the innersleeve to rotate and snap off the breakoff head. One technique therebyreduces the transfer of shear stresses to the vertebrae during thedetachment procedure. After the breakoff head is detached from thehousing, the breakoff head is removed from the patient.

The various devices, methods and techniques described above provide anumber of ways to carry out the invention. It is to be understood thatnot necessarily all objectives or advantages described may be achievedin accordance with any particular embodiment described herein. Also,although the invention has been disclosed in the context of certainembodiments and examples, it will be understood by those skilled in theart that the invention extends beyond the specifically disclosedembodiments to other alternative embodiments and/or uses and obviousmodifications and equivalents thereof. Accordingly, the invention is notintended to be limited by the specific disclosures of the embodimentsherein.

Many of the systems, apparatuses, methods, and features described hereincan be combined with many of the systems, apparatuses, methods andfeatures disclosed in the following patents and patent applications. Theentire disclosure of all of the following patents and patentapplications is hereby incorporated by reference herein and made a partof this specification: U.S. Pat. No. 6,361,488 (issued Mar. 26, 2002),U.S. Pat. No. 6,530,880 (issued Mar. 11, 2003), U.S. Pat. No. 6,648,888(issued Nov. 18, 2003), U.S. Pat. No. 6,652,553 (issued Nov. 25, 2003),U.S. Pat. No. 6,641,583 (issued Nov. 4, 2003), U.S. Pat. No. 6,554,832(issued Apr. 29, 2003), U.S. Pat. No. 6,673,074 (issued Jan. 6, 2004),U.S. patent application Ser. No. 09/821,666 (filed Mar. 29, 2001,published Oct. 3, 2002 as Publication No. U.S. 2002/0143328A1), Ser. No.09/824,411 (filed Apr. 2, 2001, published Oct. 3, 2002 as PublicationNo. U.S. 2002/0143330A1), Ser. No. 09/921,326 (filed Aug. 2, 2001,published Feb. 6, 2003 as Publication No. U.S. 2003/0028191A1), Ser. No.09/940,402 (filed Aug. 27, 2001, published Feb. 27, 2003 as PublicationNo. US 2003/0040656A1), Ser. No. 10/075,668 (filed Feb. 13, 2002,published Aug. 14, 2003 as Publication No. U.S. 2003/0153911A1), Ser.No. 10/087,489 (filed Mar. 1, 2002, published Sep. 4, 2003 asPublication No. U.S. 2003/0167058A1), Ser. No. 10/178,875 (filed Jun.24, 2002, published Dec. 25, 2003 as Publication No. U.S.2003/0236529A1), Ser. No. 10/280,489 (filed Oct. 25, 2002, publishedApr. 17, 2003 as Publication No. US 2003/0073998A1), Ser. No. 10/280,799(filed Oct. 25, 2002), Ser. No. 10/361,887 (filed Feb. 10, 2003,published Aug. 14, 2003 as Publication No. US 2003/0153927A1), Ser. No.10/658,736 (filed Sep. 9, 2003), Ser. No. 10/678,744 (filed Oct. 2,2003), Ser. No. 10/693,815 (filed Oct. 24, 2003), Ser. No. 10/693,250(filed Oct. 24, 2003), Ser. No. 10/693,663 (filed Oct. 24, 2003), Ser.No. 10/842,651 (filed May 10, 2004), Ser. No. 10/845,389 (filed May 13,2004) U.S. Provisional Applications No. 60/471,431 (filed May 16, 2003),60/497,763 (filed Aug. 26, 2003), 60/497,822 (filed Aug. 26, 2003),60/513,796 (filed Oct. 22, 2003), 60/513,013 (filed Oct. 23, 2003),60/514,559 (filed Oct. 24, 2003), 60/545,587 (filed Feb. 18, 2004),60/558,296 (filed Mar. 31, 2004), 60/579,643 (filed Jun. 15, 2004).

What is claimed is:
 1. A pedicle screw installation assembly comprising:first and second elongated bodies each having a proximal end and adistal end and an inner surface defining a passage extending through theelongated body, the passage being open at the proximal and distal endsof the elongated body and configured so that a pedicle screw isdeliverable from the proximal end through the passage to the distal endfor connection to a vertebra, the passage having a laterally facingopening along one wall of the elongated body so that a linking member isdeliverable from the proximal ends to the distal ends of the first andsecond elongated bodies for connection with the pedicle screws; and atleast one connection member connecting the first and second elongatedbodies.
 2. The assembly of claim 1, wherein the connection member ispivotably connected to at least one of the first and second elongatedbodies.
 3. The assembly of claim 1, wherein the connection memberconnects the proximal ends of the first and second elongated bodies. 4.The assembly of claim 1, wherein the connection member connects thefirst and second elongated bodies so that a distance between the firstand second elongated bodies is fixed.
 5. The assembly of claim 1,wherein the at least one connection member includes first and secondconnection members disposed on opposite sides of the elongated bodies.6. The assembly of claim 1, wherein at least one of the first and secondelongated bodies includes a cut out disposed at the distal endconfigured to receive the linking member.
 7. The assembly of claim 1,wherein the first and second elongated bodies have a length configuredto extend from a patient's skin to a vertebra.
 8. A pedicle screwinstallation assembly comprising: first and second U-shaped elongatedbodies each having a proximal end and a distal end and an inner surfacedefining a passage extending through the elongated body, the passagebeing open at the proximal and distal ends of the elongated body andconfigured so that a pedicle screw and a linking member are deliverablefrom the proximal end through the passage to the distal end forconnection to a vertebra; and at least one connection member connectingthe first and second elongated bodies.
 9. The assembly of claim 8,wherein the connection member is pivotably connected to at least one ofthe first and second elongated bodies.
 10. The assembly of claim 8,wherein the connection member connects the proximal ends of the firstand second elongated bodies.
 11. The assembly of claim 8, wherein theconnection member connects the first and second elongated bodies so thata distance between the first and second elongated bodies is fixed. 12.The assembly of claim 8, wherein the at least one connection memberincludes first and second connection members disposed on opposite sidesof the elongated bodies.
 13. The assembly of claim 8, wherein at leastone of the first and second elongated bodies includes a cut out disposedat the distal end configured to receive the linking member.
 14. Theassembly of claim 8, wherein the first and second elongated bodies havea length configured to extend from a patient's skin to a vertebra. 15.The assembly of claim 8, wherein the U-shaped elongate bodies have openchannels that face each other.
 16. A method for coupling a spinalfixation system to a patient's spine, the method comprising the stepsof: inserting a pedicle screw installation assembly into an incisionover the patient's spine, the pedicle screw installation assemblycomprising: first and second elongated bodies each having a proximal endand a distal end and an inner surface defining a passage extendingthrough the elongated body, the passage being open at the proximal anddistal ends of the elongated body and configured so that a pedicle screwis deliverable from the proximal end through the passage to the distalend for connection to a vertebra, the passage having a laterally facingopening along one wall of the elongated body so that a linking member isdeliverable from the proximal ends to the distal ends of the first andsecond elongated bodies for connection with the pedicle screws; and atleast one connection member connecting the first and second elongatedbodies; inserting first and second pedicle screws through the first andsecond elongated bodies and securing the first and second pedicle screwsto the patient's spine; passing a linking member from the proximal endsof the first and second elongated bodies, through the passages and tothe distal ends of the first and second elongated bodies; and securingthe linking member to the first and second pedicle screws.
 17. Themethod of claim 16, wherein inserting a pedicle screw installationassembly includes connecting the first and second elongated bodies witha single connection member so that a distance between the first andsecond elongated bodies is fixed.
 18. The method of claim 16, whereininserting a pedicle screw installation assembly includes connecting thefirst and second elongated bodies with first and second connectionmembers so that a distance between the first and second elongated bodiesis fixed.
 19. The method of claim 16, wherein the connection member isdisposed on outer surfaces of the first and second elongated bodies. 20.The method of claim 16, wherein the connection member is pivotablyconnected to at least one of the first and second elongated bodies.